Once it was determined that a loss on time occurred the game is over and the result stands. If the opponent didn't want the time claim then the TD shouldn't have been called over.
GM loses on time after draw offer?

Some TDs would allow the potentially winning player to convert the game to a draw if that was her desire. A request for verification of the move total or a possible time forfeit does not take the game result completely out of the hands of the players. An erroneous move calculation does not give the TD the full and irrevocable right to have power over the game result.

I think he's right. If not by the rules then morally.
Offering a draw after the flag had fallen is trying to change the correct result.

Only legalistically as the moral thing to do is often to permit all human factors to be considered. Ultimately a game result is in the hands of the players unless they have violated more serious rules through illegal disturbances, etc..
Sergei Kudrin lost to AKSHITA GORTI over the weekend in Stamford at the tournament. Kudrin thought he was on his 41st move, but instead was on the 40th. Gorti called the TD, and then when it was found he had lost on time, she offered him a draw anyway. TD Immelt denied the draw. Was he wrong??