Thought I'd comment as a very casual roadgeek whose local exit is one of the new 37s. For several days, the leading edge of the renumbering going northbound was old 25A/B (new 39B/C). So there was a 39B and 39C northbound, but no 39A (as it was still 24). Going southbound, though, the leading edge was 37B/C/D (old 22A/B/C), so not only was there a 37B, C, and D, without 37A,
but the exits were numbered differently depending on which direction you were going! (Yesterday had a similar situation in the opposite direction, as the renumbering moved southward on the northbound side, but stayed put on the southbound side, so exits 19, 20, and 21 going southbound were exits 37A, 36B, and 36A, respectively).
Also, for what it's worth, I noticed that they were (and maybe still are)
staging the signs before installation up in Massachusetts at the rest stop near NB MM 10.