stalemate
Do you mean the insufficient material rule? I think they sort of follow USCF guidelines, rather than FIDE. Probably something to do with the programming. You could probably research it...
There are 31 pages of threads on this...Enjoy!
https://www.chess.com/forum/search?keyword=insufficient+material
If you are talking about the following game, it is black's turn to move. Black has no legal moves. Black is not in check.
That is the definition of stalemate and every site and all official chess play calls that statemate and a draw.
https://www.chess.com/live/game/4821040366
Instead of pushing your pawn, Nc5, Qc6, Qc8 or Bc8 were all mate.