What is the difference b/w @form value and explicitly mentioning the component Ids in render attribute of ?

Question

Consider the snippet:

<h:form>                                  
    <hr/>
    <h:panelGrid columns="3">
                Name:
        <h:inputText id="nameId" value="#{ajaxBean.name}" 
                     validator="nameValidator" 
                     f5:placeholder="Enter your name ..."/>
        <h:message id="msgNameId" showDetail="true" 
                   showSummary="true" for="nameId" 
                   style="color: red;"/>
                Surname:            
        <h:inputText id="surnameId" value="#{ajaxBean.surname}" 
                     validator="nameValidator" 
                     f5:placeholder="Enter your surname ..."/>
        <h:message id="msgSurnameId" showDetail="true" 
                   showSummary="true" for="surnameId" 
                   style="color: red;"/>            
    </h:panelGrid>

    <h:commandButton value="Submit">
                <f:ajax execute="@form" 
                        render="@form" listener="#
                        {ajaxBean.upperCaseNameAndSurname()}"/  
   </h:commandButton>

   <h:commandButton value="Cancel">
                <f:ajax execute="@this" 
                        render="@form"/>
   </h:commandButton>  
   <h:commandButton value="Clear/Reset">
                <f:ajax execute="@this" 
                        render="@form" 
                        listener="#{ajaxBean.cancelNameAndSurname()}"/> 
   </h:commandButton>
</h:form>  

resetValues= "true" seems to work only if one mentions the component ids explicitly inside the render attribute of the <f:ajax> for the Submit button.

i.e render="nameId msgNameId surnameId msgSurnameId" rather than render="@form"

What exactly is the difference b/w these 2 forms?

The invalid values are still there after re-render if the value is (@form) for render attribute for Submit button.

I definitely remembered one of the comments by BalusC,

When validations phase has failed due to a conversion or validation error anywhere, components which successfully passed validation will return local value and components which failed validation will return submitted value.

If the name is valid and the surname is not (or any other combination involving invalid values), then after submit and clear/ reset, the input field*(i.e the valid field)* for the name is not cleared. Even though the whole form was re-rendered, I see only the field for which validation failed was cleared. Why?

Does the above comment signifies some relation with the above problem?

The cancelNameAndSurname method just do this thing-

name = ""
surname = ""

I know for sure that one of the solutions to resolve this is -

       <f:actionListener type="org.omnifaces.eventlistener.ResetInputAjaxActionListener"/>