UIViewRepresentable updateUIView() strange behaviour when using .sheet()

Question

I just found some strange behaviour of SwiftUI's UIViewRepresentable. I'm not sure if this is a bug, or my mistake in understanding SwiftUI. I've made small reproduction to show the problem.

I created UIViewRepresentable for MKMapView:

import SwiftUI
import MapKit

struct UIMap: UIViewRepresentable {
  
  func makeUIView(context: Context) -> MKMapView {
    let map = MKMapView(frame: .zero)
    map.delegate = context.coordinator
    return map
  }
  
  func updateUIView(_ map: MKMapView, context: Context) {
    print("Change!")
  }
  
  func makeCoordinator() -> UIMapCoordinator {
    return UIMapCoordinator(self)
  }
  
  class UIMapCoordinator: NSObject, MKMapViewDelegate {
    var parent: UIMap
    
    init(_ parent: UIMap) {
      self.parent = parent
    }
  }
}

Then I create really small wrapper for this representable:

import SwiftUI

struct MapWrapper: View {
  var body: some View {
    UIMap()
  }
}

Finally I'm using it in ContentView:

import SwiftUI

struct ContentView: View {
  @State private var showSheet = false
  @State private var showButton = true
  
  var body: some View {
    ZStack(alignment: .bottom){
      MapWrapper()
      HStack{
        if showButton {
          Button(action: { showSheet = true }){
            Text("Show Sheet")
          }
          .foregroundColor(.yellow)
        }
        Spacer()
        Button(action: { showButton = !showButton }){
          Text("Toggle Button")
        }
        .foregroundColor(.yellow)
      }
    }
    .sheet(isPresented: $showSheet) {
      Text("Sheet content")
    }
  }
}

I have two clickable elements in ContentView - one for opening a sheet, and another for hiding button (just to see state change). Opening sheet (changing showSheet to true) causes updateUIView being called ("Change!" is printed in debug console), while changing showButton doesn't do that. It looks like opening sheet changes state of MapWrapper(?). Is this behaviour correct?