The tenchess counterargument doesn't work in the context of Elo (from which chain lengths are derived).
A has 150 more Elo rating than B in chess. Elo says A has a 2/3 EV on the game result, and B has 1/3.
In tenchess, A will get 20/3 points on average and B will get 10/3 points. A will have more points than B in 79% of tenchess games, but the Elo ratings will not change. Elo doesn't consider winning and losing as binary. (This is why draws behave sensibly.) Just as a tie between these players cause A to lose rating, so too would a marginal win from A.
I think I wasn't clear enough. Here is how you play a game of tenchess. (1) Play ten games of chess. (2) You get 0 points if you won fewer chess games than your opponent, 1 point if you won more, 1/2 a point if you won the same number.
In particular, you don't get the total number of points you'd have got by playing the chess games individually. You get 0, 1/2, or 1. In particularly particular, A doesn't get any fewer points from a marginal win than from a blowout. (Just as, when playing chess, you don't get fewer points from taking 100 moves to grind out a tiny positional advantage than from a 20-move brilliancy.)
So A and B don't get 20/3 and 10/3 points on average from a game of tenchess; that's the number of "chess points" they get on average, but the average of the number of chess points isn't a thing that actually matters when they're playing tenchess.
(If A wins 2/3 of the time at chess and they never draw, then it turns out that A gets about 0.855 points per tenchess game.)
A has 150 more Elo rating than B in chess. Elo says A has a 2/3 EV on the game result, and B has 1/3.
In tenchess, A will get 20/3 points on average and B will get 10/3 points. A will have more points than B in 79% of tenchess games, but the Elo ratings will not change. Elo doesn't consider winning and losing as binary. (This is why draws behave sensibly.) Just as a tie between these players cause A to lose rating, so too would a marginal win from A.