I'm not a licensed math surgeon, but I think your math is wildly optimistic in favor of Microsoft due to how the subscription totals are actually distributed per price tier.
I don't doubt that they did a lot of math to figure out an acceptable level of churn for this change, I just don't think it's nearly as generous and wide as you're calculating.
There probably is a very real churn limit that they're trying to avoid, and my hunch is that there exists a breaking point that could be hit with an aggressive and sustained boycott / cancellation spree, but again, I'm not a math surgeon so I could be wrong. That's just my gut feeling.
That's currently in QA as we speak... Slated to go live Q1 2026.