Hmm. I have a question...
The same document for 12.0 say Generation 1 (Release 12.0, Issue 19, April 2024, page 52), while the one for 12.1 say Generation 2 (Release 12.1, Issue 24, October 2024, page 50).
Obviously, I did not install or upgrade a server edition with 12.1 on Hyper-V yet, but in the past I tried to install 11.x with Generation 2 which doesn't work.
However, I had a problem with not booting up after upgrading a server edition 11.1.3.1 to 12.0 using the upgradedisk.vhd.
I had to revert to the snapshot. The plan is to give it another try when 12.1 is available.
Maybe, the "Generation 2" is a typo. Because you cannot change the machine version once it is running.
So how about upgrades? Shall we somehow change from the R11.1 Gen1 to an R12.1 Gen2? How?