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.
Nowadays that isn't any longer the case, linting is also performed, at least on Visual Studio proper.
https://learn.microsoft.com/en-us/cpp/ide/cpp-linter-overvie...
Yeah, this extension is almost the default choice for vscode https://marketplace.visualstudio.com/items?itemName=ms-vscod...