Lenovo might have changed its mind about releasing a SteamOS version of the soon-to-be-announced Legion Go 2. The handheld is expected to run Windows out of the box, but an official image has shown it running SteamOS. Hence, Lenovo might release the handheld in two OS versions, as it did with the Legion Go S.
I think you may be thinking of Legion Go S. This is Legion Go 2. As far as I’m aware, the fact that it even exists is new.