MCS Electronics bought their VID before the USB-IF cartel changed their rules to forbid resale. MCS is in the EU, which I'm sure you're aware takes a dim view of unilateral ex post facto contract revisions.
Of course. However, even though with those contracts I wouldn't be so sure, because the fact that a company resides in the EU doesn't automatically mean the contract is also being governed by EU law. Companies don't generally have the same protections as consumers do and it is very common to find a clause that the contract is being governed by the law of some US jurisdiction. If both sides agree on that, it is completely legit. The same if the contract stipulates that it can be revised in the future.
Now whether that's the case I don't know, I didn't sign any of these myself.
The practical effect of "revoking" a VID is nonexistent, since they can't resell a revoked VID to anyone else. They didn't think their goofy get-rich-quick plan all the way through.
Right, but that doesn't mean hw vendor would want to use a revoked range. Reassigning the VID is not the only possible problem - it could also spectacularly backfire should e.g. USB-IF make a deal with Microsoft and they start blocking devices from such ranges in Windows in the future as a safety/security measure. Would it be incredibly stupid thing to do? Yes. Did they do even dumber things in the past? You betcha ...
And for a hobbyist building a widget for themselves it really doesn't matter. Just pick a VID:PID pair that doesn't conflict with something else you have.