The documentation says:
Anki checks the first field for uniqueness, so it will warn you if you enter two cards with a Front field of “apple” (for example). The uniqueness check is limited to the current note type
Well, you can create two notes with a front field of “apple” when the note types are different and then, when you have done that, you can change the note type afterwards to the same type of the other “apple” note.
Anki will not complain. It will only change the backgroundcolor of that field to red, but it’s possible to use the notes when learning. There is nothing, that will prevent you from doing so.