It has no relation to Michaels; it's an Unusual 2NT and GIB correctly describes it as such. Thorvald just put the wrong description in above.
thorvald, on 2022-October-09, 14:14, said:
I wonder how strong a hand GIB needs to bid other than 3♣ with longer ♣ than ♥.
Non-vulnerable you can give it Ax.AKQ.AQxx.xxxx and it'll bid 3
♣ without simulating. Give it an extra Jack, and it will simulate before leaping to slam.
The book bid in the earlier version of GIB was also 3
♣, but that was mainly intentional / not a problem - the only specific continuations it defined after U2NT was to give preference to the longer suit (or occasionally bid 3NT); everything else was meant to come from simulations, which makes sense. (There is a weird quirk in the database that tells it not to count a jump to 4M as a book bid in many situations when there are chances of slam, but it's allowed to pick this when simulating, so that's not really a problem.)
But they must have really messed some bid priorities / simulation spots up, as back then it would choose from a range of 4-5 different continuations including game in hearts as you'd expect.