filename Syntax search filter does not work as in docs

Summary

When searching code with Advanced Global search enabled, according to https://docs.gitlab.com/ee/user/search/advanced_search_syntax.html#syntax-search-filters it should allow literal filename filters but it does not.

Steps to reproduce

After indexing the content, search for a file with its complete name with the filename filter as in:

Although searching with the filename without the extension provides the expected results:

What is the current bug behavior?

filename search filter does not work as explained on the docs.

If the search does not specify any content (* filename:product path:cbng-product-xml) the results are even weirder:

Among the results there is a file which is not even named product in any way.

It looks like the filename filter is used for searching content as well.

Right now the only way to find a file with a specific name is by using the path filter.

What is the expected correct behavior?

Searching with the literal filename filter should provide results from files with that name.