I Suppose from the Hand of 2S Bidder you See, He was Clearly Thinking it is Forcing ( Probably to Game ) Opener 2C Bidder Must Have Forgotten ( Many Do Play 2H or 2S on Precision 2C Opening bid to be NF Passable ) So Gave Meaning to be Non Forcing which everybody on Table Herad. Now 2C Opening is done with min 9 HCP also if having Good 2 Suiter Shape. So 2S Bidder has to Judge the Range 9/10 HCP or 14/15 HCP, which in absence of UI was not possible for him. with his Given Hand will he dare to Probe Slam if 4S bid was Made , he not having any Clue, here he Heard Passable and Still Pd Bids Game, Has to have Maximum Hand ( UI )