That was a total surprise for me. Since the TX had more fees than 24 sats/byte, I can't think of any possible reason for excluding it.
I think that would mean they are not including the backlog of transactions they have based on the higher fee rate that the user used, maybe there's another mechanism to it or they are just picking randomly; i am not sure which it is. Anyway, since the message you got is "Accelerating this transaction", they'll prolly definitely get to yours sooner or later.