As far as I'm aware the vanilla Intellisense (e.g. error squiggles and warnings while typing) isn't doing proper static analysis only simple syntax error checks.

And while clang-tidy is integrated with the MS C++ extension, it needs to be run manually, or automatically on file save/open (see: https://devblogs.microsoft.com/cppblog/visual-studio-code-c-...) - I guess it's too expensive to just run in the background while typing.