That may not be noticeable if your hardware is too fast, I started to see a problem when I was working on slow hardware, but even under wine with ext4 on sata drive or usb3 drive, that won't be visible, but if you use usb2 port, and/or an old drive, and/or a shared network, or whatever which slow down I/O you should start to notice that "looking for unknown sets" phase will be slow on empty directories, and will accelerate on zip files...
I tried ntfs and ext4 (but not fat), wine and native, local and shared network... the problem is present everywhere at different degrees when using slow hardware
Another odd problem on slow hardware (in my case it's an Intel Celeron J800 with 2GB DDR3@1333) especially with wine, when I click on "Scan" or "New Scan" with a profile that use a full mame software list, I have to wait lot of minutes (around 30mn) before the progress bar start to show with "Creating HashTables"... During this time the only thing I see is cmpro's memory usage growing slowly from 270MB up to ~1GB , no disk io, and its process at 100%, I suppose you are making many small struct allocation in memory for each rom/set... is it possible to look at that part to see if it's possible to optimize? Please note that this 30mn wait does happen with a freshly started cmpro, it does not happen if I start a scan again, or if I reload the same profile
Thank you