Msvc treats inline as a hint [0] , GCC is ambiguous [1] but I read it as utilising the hint. My under of clang [2] is that it tries to match GCC.
[0] https://learn.microsoft.com/en-us/cpp/build/reference/ob-inl...
What the OP is saying is that it has a use to satisfy (https://en.cppreference.com/w/cpp/language/definition) and in that case it is not optional and not ignored by the compiler. Whether it will "actually" inline it is another matter, that is optional.
Funnily, the inline keyword actually has a use, but that use isn't to tell the compiler to inline a function. The use is to allow a function (or variable) to be defined in multiple translations units without being an ODR violation.