Oh, for all practical purposes I would say that a buy-in-beta is early access. I mean, there's no difference from a developer-player transaction point of view.
But in terms of "have we ever done the Steam Early Access program," which is a very specific thing with a lot of specific connotations, requirements, blah-de-blah: no we have not.
On the one hand it doesn't make any difference, and I'm not trying to dodge saying we've done it before. But on the other hand doing an actual "Early Access on Steam in the modern sense of the actual thing" is new to us in a literal sense, so there are some bits there that are relevant for a practical point of view.