Playtonic have always referred to Rexto's arcade titles as multiplayer. This continues to be the case with their recent update and what Rextro says this accompanying trailer.
At 20:30 in this video they refer to the arcade machines as unlockable multiplayer ones https://m.youtube.com/watch?v=rStKYUD_3GQ
The Steam post does appear to contradict this. Could be a mistake.