No. Every 1600 player blunders. In the case of lost positions where you want to work on your game, mention it. I've done it several times and my opponents haven't taken issue-when I'm clear I'd like to play on to where the end (they win) is fairly obvious, and my intent is practice.
Of course, a blunder by the opponent at this stage can turn the game 180 degrees. At 1600, almost anything can still happen.

I won to a resign last week and was frankly shocked. He blundered a rook and immediately resigned -- even though we still had queens on the board and he had center board control and a passed pawn!
I think there's a lot of pressure on this site to resign when you're down significant material but I think the decision needs to include player skills. I'd certainly expect that a blundered Rook against a GM would result in a loss but we were both mid 1500s and fully capable of making errors.
I'm playing a game right now where I ended up down a Rook but my opponent quickly blundered a B and now I'm looking at BB vs BR and I've got 6 pawns to his 3. If I'd resigned when I lost my R that would have been a mistake.
I have resigned games but only when the outcome is obvious. But it's not always obvious to me and point counts alone are not always indicitive of a loss - a passed pawn is often worth a minor piece.
I also need to work on my endgame - so I may not resign so readily just to get the experience.
So am I being inconsiderate not to resign when down material? I don't think so - especially at my level of play.