Tried using C# but has yet find a way to get the information this way either, if at all possible?
I do a demo with Microsoft.Azure.Management.RecoveryServices.Backup 2.1.0-preview. It works correctly on my side.
How to create the auth file please refer to auth file formats.
subscription=########-####-####-####-############
client=########-####-####-####-############
tenant=########-####-####-####-############
key=XXXXXXXXXXXXXXXX
managementURI=https\://management.core.windows.net/
baseURL=https\://management.azure.com/
authURL=https\://login.windows.net/
graphURL=https\://graph.windows.net/
Demo code
var subscriptionId = "subscriptionId";
var credentials = SdkContext.AzureCredentialsFactory.FromFile(@"Auth file path");
var client = new RecoveryServicesBackupClient(credentials) {SubscriptionId = subscriptionId };
var result = client.BackupJobs.List("vaultName", "resource Group").First();
var workloadType = ((MabJob) result.Properties).WorkloadType;

Packages.config
<?xml version="1.0" encoding="utf-8"?>
<packages>
<package id="Hyak.Common" version="1.0.2" targetFramework="net461" />
<package id="Microsoft.Azure.Common" version="2.1.0" targetFramework="net461" />
<package id="Microsoft.Azure.Common.Dependencies" version="1.0.0" targetFramework="net461" />
<package id="Microsoft.Azure.KeyVault.Core" version="1.0.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.AppService.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Batch.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.BatchAI.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Cdn.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Compute.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.ContainerInstance.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.ContainerRegistry.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.ContainerService.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.CosmosDB.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Dns.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.EventHub.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Graph.RBAC.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.KeyVault.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Locks.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Monitor.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Msi.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Network.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.RecoveryServices.Backup" version="2.1.0-preview" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Redis.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.ResourceManager.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Search.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.ServiceBus.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Sql.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.Storage.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Azure.Management.TrafficManager.Fluent" version="1.8.0" targetFramework="net461" />
<package id="Microsoft.Bcl" version="1.1.9" targetFramework="net461" />
<package id="Microsoft.Bcl.Async" version="1.0.168" targetFramework="net461" />
<package id="Microsoft.Bcl.Build" version="1.0.14" targetFramework="net461" />
<package id="Microsoft.Data.Edm" version="5.8.2" targetFramework="net461" />
<package id="Microsoft.Data.OData" version="5.8.2" targetFramework="net461" />
<package id="Microsoft.Data.Services.Client" version="5.8.2" targetFramework="net461" />
<package id="Microsoft.IdentityModel.Clients.ActiveDirectory" version="2.28.3" targetFramework="net461" />
<package id="Microsoft.Net.Http" version="2.2.22" targetFramework="net461" />
<package id="Microsoft.Rest.ClientRuntime" version="2.3.9" targetFramework="net461" />
<package id="Microsoft.Rest.ClientRuntime.Azure" version="3.3.10" targetFramework="net461" />
<package id="Microsoft.Rest.ClientRuntime.Azure.Authentication" version="2.3.2" targetFramework="net461" />
<package id="Newtonsoft.Json" version="6.0.8" targetFramework="net461" />
<package id="System.ComponentModel.EventBasedAsync" version="4.0.11" targetFramework="net461" />
<package id="System.Dynamic.Runtime" version="4.0.0" targetFramework="net461" />
<package id="System.Linq.Queryable" version="4.0.0" targetFramework="net461" />
<package id="System.Net.Requests" version="4.0.11" targetFramework="net461" />
<package id="System.Spatial" version="5.8.2" targetFramework="net461" />
<package id="WindowsAzure.Storage" version="8.1.4" targetFramework="net461" />
</packages>