Same issue here in 18.104.22.16801. We use a SQ server in our Jenkins pipeline setup. Administration is done via the administration web interface.
When entering a pattern under Analysis Scope > Coverage Exclusion, the matching files are NOT excluded from code coverage (unexpected). In our case, coverage remains at about 46%.
When entering the EXACT same pattern under Analysis Scope > Global Source File Exclusions, the matching files are no longer analysed and are NOT taken in account for code coverage (expected). In our case, coverage increases to 95%.
Hope this helps.