The picture posted on the airport's social media pages advertising this feature on 15/12 suggests that they're the very same e-Gates used for Thai nationals. Unclear if it means in practice immigration has delayed implementation or if airport staff directing people to go left or right based on their passports simply have chosen to not openly advertise this feature.

Maybe next time if there is no one directing traffic and/or you are a type of foreigner that can easily blend in with Thai passport holders, you might give it a go and report back to the rest of us? (Well, the non-Thai passport holders here anyways. I selfishly don't mind if this feature never gets implemented in practice.)