Actually, I was well aware of exactly that. I remember observing during the discussion with the other TD that a pawn can change things not only by getting in the King’s way or by threatening to promote, but also by simply being able to move when it would otherwise be stalemate. Also, the rulebook wouldn’t have bothered adding the clause about forced mates unless that possibility existed. My memory is a bit fuzzy (this happened back in March), but I think Black may have had more than just King and pawn (i.e., there might have been more than one pawn, or Black might even have had a Knight), which makes a forced mate for White even less likely. In any case, it was pretty clear to both me and the other TD (and to several of the spectators) that there was no forced mate. We just used Stockfish to make sure.
Note that 14E says nothing about what material the time-forfeiter has. It considers only whether the other person has “mating material”. And in this case, the more material Black has, the less likely it is that two Knights constitutes “mating material” for White.
Another thing to consider is that “plausible losing move” can be a very hard thing for a TD to judge. If a move looks “plausible” to me, that’s probably because I don’t see that it’s a losing move. If I do see that it’s a losing move, I wouldn’t consider it plausible. And a stronger player than me might immediately see that it loses and say “That’s not plausible at all – it just loses!” I like my rules to be more clear-cut than that. I don’t like to have to play guessing games with positions that may be beyond my ability to evaluate correctly.