The closest thing that comes to mind was Mozilla's switch to "Web Extension" browser add-ons, destroying about a googol of Firefox apps in one fell swoop, but that was just one company's unilateral decision - and it didn't entirely work, due to Firefox being open source. Given Flash's frequent security and privacy issues, I can understand the decision, but AFAIK it's pretty much unprecedented. The entire PC software industry, including Adobe, Google, Microsoft, and Mozilla, (and probably other big players like Apple too) collaborated in a multi-year effort to render a commonly-deployed Web technology useless. Switching topics slightly, I find this whole Flash imbroglio striking. But even the catalog now needs a local proxy for IE8 to connect, since it switched to modern security protocols. About the only site that works better under IE is Microsoft's Update Catalog, since you can select multiple updates with IE then download them all with a single click (other browsers require separate clicks to download each update). IE9/ Vista SP2 is practically worthless for most sites of 2021, including MSFN Knowing Microsoft, it's likely there's a registry entry somewhere to turn the bloody thing off, but I don't know that for sure. But of course, if you do have a working Flash version installed, the Web pages do work, so the warning bar is just a nuisance. Since it was added after Flash EOL, my guess is that it was intended to tell users why these Web pages don't work any more. You can dismiss the warning, and at least as of the July update roll-ups, if you have a working ActiveX Flash version installed, Flash content still works.
It's not a time bomb just a warning bar that pops up if you browse to a site that uses Flash content, reminding you (once again) that Flash is EOL. IE 8 for XP hasn't been updated since PosReady '09 EOS, so no change for XP users). I suspect very few folks use Internet Explorer with Flash anymore, but for those few, last March Microsoft added a "security feature" to IE 11 (and I think IE 9 for Server 2008 perhaps a Vista user can confirm or refute that.