draw by insufficient material strange rule

Here is an example of why not using normal fide rules (that is allow the draw if and only if there is no possible checkmate) is bad :



black gets checkmated on the next move, let his time run and draws

where and when black is checkmated in the next move!?

As discussed here recently:
http://de.lichess.org/forum/lichess-feedback/lichess-computer-system-error?page=1

ah yes sorry black is checkmated in next 3 moves

However, in this case :


the server gives a win (in a position that would be a draw without the h7 pawn)
seems like these are arbitrary rules