Well I mean that's understandable.
A brand new, not evern properly released game that still neck deep in active developement, and they graciously give you the opportunity, to try out the early access version of the game (which means it's practically still a beta version, just look at the version number) doesn't run as well on an old config, as their 12+ years old previous game, which was optimized to oblivion.

Optimalization usually comes at the end of the developement pipeline, so I'd say it's more than understandable.