A bit off topic, but unit test coverage trivializes the work that goes into conducting a migration. Unit test coverage really only pertains to upgrades. A migration is not synonymous with an upgrade. Migrations are serious work that typically span entire ecosystems.

When I mentioned "the numbers" I wasn't hinting at unit test coverage. I was giving examples as to what the numbers could be. Obviously OP should ask lots of questions about all of the software running on a legacy kernel.