I think it is ok since time management is part of chess.
it depends on the time control.
if both players have 2 hours to start with.
and one player has 1 minut left and I have 30 minutes left.
I think it is fair to reject the draw.
but again it depends on the position if both have K+R vs K+R I wouldn't play on.
What is the ettiquet rule of playing out a drawn game when your oppenent is dangerously low on time? Is it unsportsman like to deny the draw play though the drawn position and then throw the game with 5 seconds left on the clock?
The position was clearly a drawn position, at the time it was offered.