I don’t usually bug people about this but you mean “MSIs”, not “MSI’s”. They mean different things in this context.

But if you're using it for yourself you wouldn't want to put it in system32.

There was a looong period of time where a lot of developers felt entirely free to drop whatever they wanted into c:\Windows, System, System32, whatever. It's a big part of what led to windows getting a reputation for being poorly behaved/crashy/slow over time [leading to a lot of "have you tried reinstalling windows?" recommendations]

Yes but I think that's separate from a newer installer using one of these newer runtimes.