Personally I prefer wording referring to (no legal moves available to deliver mate) instead of (insufficient mating material) because that would include totally blocked positions, but that would also require a change to 7c (and nothing wrong with adding that change).
If you just use the phrase “no legal moves available to deliver mate”, wouldn’t that exclude situations such as K+N vs K+R? K+N (without a forced win) is considered insufficient mating material but there are “legal moves available to deliver mate” in a K+N vs K+R ending.
That’s really a flaw in the US chess rules, that that is listed as “insufficient to continue” but not “insufficient to win on time”. I cannot for the life of me think of a position that should be in first category but not the second.
I guess as part of the blitz rules ADM, the definition of mating material in blitz rule 7c would need to be revised since it’s different than the definition of mating material in rule 14E.
The blitz rules state that a game is won by a player “7c.) Who correctly points out that the opponent’s flag has fallen first, at any time before the game is otherwise ended, provided the player has mating material. Mating Material consists of (at a minimum) two minor pieces, a pawn, a rook, or a queen provided it isn’t a position where one could claim a draw under rule 8.”
I wonder if the statement “provided it isn’t a position where one could claim a draw under rule 8” means that the K+N+N provision from rule 14E3 would apply and be considered insufficient mating material in blitz. This seems like a very clunky way to try and explain all of this.