Sheet codenames work in array but not named range

I would be grateful if someone could tell me why this works:

Sub SheetArrayTest()

Dim wShtArray() As Variant
Dim Sht As Variant

wShtArray = Array(Sheet01, Sheet02, Sheet03)
 
    For Each Sht In wShtArray
      Sht.Visible = True
    Next

End Sub

but this doesn't (throws "Object doesn't support this property or method"):

Sub SheetRangeTestA()

Dim Sht As Variant

    For Each Sht In Range("MainSheets")
       Sht.Visible = True
    Next    

End Sub

I am guessing that the array is passing the sheet codenames as objects and that's what is needed. If so, what do I need to do to get the same sheet codenames held in the named range "MainSheets" to work in the same way? I have tried reading "MainSheets" into an array but that doesn't work.

Thanks.