I think they are also trying to tell us this is the best its going to be so vote yes and lets get on with it
That is part of it. the final vote is public information. If a large number of workers vote and the contract passes, Yellow can show their customers that the workforce is behind this agreement and is willing to do what it can to service the customer. With no customers there is no business and with no business there is no union needed to protect the workers that no longer have jobs.