How to stop showing up function declarations from excluded directories?

Hello. I have standard Symfony project with tools/ directory containing additional vendors and tools like phpstan, deptrac, phpcsfixer etc used when developing. It has its own composer.json and composer.lock. When I try to click on PHP standard function in my code, to see its declaration I get this:

Whole tools/ directory is excluded in project

Inside IDE PHP settings I cannot exclude tools/ tho because exclude button is disabled. 

Here is my Directories settings

And composer settings

Tried to remove invalidate cache etc but nothing helps. Any idea what is going on? Is it a bug? Thanks