When you have done enough C++ you don't need to fire up compiler explorer, you just use local variables to avoid aliasing pessimisations.

I also wrote about this a while ago: https://forwardscattering.org/post/51

I think this might not be a shortcoming of MSVC but rather a deliberate design decision. It seems likely that MSVC is failing to apply strict aliasing, but that it's deliberately avoiding it, probably for compatibility reasons with code that wasn't/isn't written to spec. And frankly it can be very onerous to write code that is 100% correct per the standard when dealing with e.g. memory-mapped files; I'm struggling to recall seeing a single case of this.