@mitu First of all thank you for taking the time to check and make a patch.
Glad i managed to point you to the right info

I want to confirm that your patch on latest dev (2.12.0RP-DEV) is working as supposed to and did in the past.

I ve tested 2 systems, the AGS and PC98 for similar setup (upper case extensions and deleted from es_systems.cfg)
Both show ONLY what is in lower case extension and hides the upper case ones (deletd from cfg)

My kind regards and thank you again!