The problem with poker is that there is money to be made from having a strong AI so there is 0 incentive to release it. What's publicly available are solvers (which solve game abstractions similar to the full game but don't play themselves) and shitty bots.

As a commenter above noted, this work is about generality, being able to play every game, and not being the best at every game.

The abstract claims they beat the "strongest openly available agent in heads-up no-limit Texas hold'em poker". To a non-expert that certainly sounds like they're claiming to be the best

"Openly available" is a strong constraint that's mentioned explicitly.

As noted before, the reason for including old tech is to look better. Why not mention the current state of the art and show that with a general player we can come close to this results?

This is just benchmark cherry picking and does not reflect real performance or comparison.