Yep. Scummy, even for Microsoft. Too bad their EULA blocks class action.
They were selling it until October 2021, so it's not some ancient system. By building a time bomb into it, they misrepresented what was effectively a $50/year subscription as if it were a $229 purchase. Should be a slam dunk case, but it won't be.
I don't think this can be the case given that the program will keep working in reduced functionality mode. This wouldn't be possible in the situation you describe.
After all, a computer with the date set to 2021 will still function...