Saying "yeah, we promised you 10 years of support, but if you just bought yours the last two years of that will only be supported if you switch to a completely different OS. But happily some of our devices have a direct migration path (if that's not yours, deal with it). Better hope the features you need will be available in our new OS by then, because right now they are not" is a major rugpull and not reasonable at all
We don’t have any details about what the upgrade path will look like and it probably hasn’t been implemented yet, so this is all speculative.
If they didn’t do an OS change, they could still evolve it a lot over 10 years. Chrome could evolve too. You’re trusting the vendor to not screw up your workflow either way.
Of course, I don't think any schools are getting 10 years out of a chromebook, but some businesses might be.
The practical issue in this case appears to be that GoogleBooks branding is meant to indicate they are good at running Gemini and other Google AI technologies. Chromebook aren't.
I doubt the entity called Google is of one mind about any of this.