This could be all speculation, but part of the reason for not re-recording "Put On Your Sunday Clothes" with Carol's line flub may have many reasons.
I was once told that when recording cast albums, whoever is in charge usually likes to get the Ensemble and Company numbers out of the way first, and leave the solo's and duet's (with less people) 'til the end. That way, they don't have to pay everyone the same. "Put On Your Sunday Clothes" is a company number - and not a short one - and Ms. Channing's mistake happens right in the middle of the song. Perhaps they just didn't find it necessary to record again and take up more time.
Also - the early coming-in gives us something to write about on message boards 40+ years later! And it's charming.
I'm as jumpy as a virgin at a prison rodeo!