I'm not too worried here, since you don't come to a different main blockchain sequence with assumeValid=0 or some other block hash or default assumeValid of your particular Bitcoin Core version.

I get your and LoyceV's message about "Don't trust, verify!" and in many cases I follow this mantra. In my IBD experiments, especially with a Raspi involved, I wasn't too eager to stress test such a device too much (my patience has limits). So in this case my "from scratch" may not be your "from scratch", no quarrals about that.

Maybe more scientific IBD experiments needed...

At some point I have to draw a line for myself. My code reading and comprehension abilities for Core's code are limited. At some point I have to trust others who are better at it and audited Core enough to sign it off. I can't do the "verify!" part on my own for Core. I have to trust it (and others) to implement Bitcoin protocol properly, including to not mess up with default assumeValid. Even with default assumeValid a lot of validation is still done with ancestor blocks but some expensive validation is skipped.

Maybe some future me will check and verify that the main chain isn't any different with assumeValid=0 from its default setting.