In all honesty, I feel the (NOT so) Smart Scan, is like many other on-demand scans, much depreciated in an on-access, resident antivirus program.
Whilst there are other areas that are covered by this scan, that aren't ordinarily covered in on-demand scans. For me the smart scan is more of a sales opportunity for avast to try and sell you other avast paid products.
The reason I say it is NOT so Smart are for the reason you have just mentioned, it either doesn't check of doesn't consider what you have, it is no doubt going to offer you Avast Premium with its firewall option.
I have paid firewall on my XP system and like Bob I use the Windows firewall on my Win10 laptop.