I forget the nuance but yes, so long as there were 2 kings of a color they were treated like other pieces until 1 remained I think.
The promotion of an opponents piece could end in a game where you promote your pawn to their knight which becomes a checkmate as the pieces were organized in a way that blocked the king.
The promotion of an opponents piece could end in a game where you promote your pawn to their knight which becomes a checkmate as the pieces were organized in a way that blocked the king.