While technically correct, the change in 716a70d leads to false positive reports for code like this:

$abc = $request->query->get('abc');
Assert::notNull($abc);
expectString($abc); // 💥 Parameter #1 $str of function expectString expects string, bool|float|int|string given.

AFAIK Symfony never converts query string values from string to other types. So unless the $defaultValue argument is specified, InputBag::get() always returns string|null. And if $defaultValue is specified, the return type should be string|T where T extends string|int|float|bool|null.