No need for the apology. Ranting is what the internet was designed for. That, and cats.

Your irritation will subside over time but your approach to the future is correct if you're LTP. You should only stay at Bonvoy hotels that meet your requirements and provide added value than the off-brand next door rather than through some misguided loyalty. You don't need the nights any more.

To your last point, I believe that the computations are only done at the point of posting on the Bonvoy IT system and not at the point of reservation or indeed check-in. It would of course be possible for Marriott's IT department to write some code that checked each reservation as it was made for any potential posting conflicts and raise a red flag to the member there and then. But it's not how it's done and I don't suppose anyone at Bonvoy would even consider the investment in this piece of coding given that it's not their problem and at worst it could reduce the number of reservations that are made. Which, of course, is also the outcome that you have arrived at.