Well I'm not the one in charge of NATO. If I was the leader of America, I'd want to commit hundreds of tanks as well as enough artillery to support such a formation, because tanks in storage at home are doing nothing, might as well use them even if they won't be very efficient. Assuming I want to win the proxy war or at least get more leverage to my side.
But clearly for them there is some sort of concern among American ranks, either a lack of faith in own capabilities or a lack of trust in Ukraine.