This link has some general info as to why some items might not be immunized:
https://www.safer-networking.org/faq...-immunization/

The link posted in my post above seemed to point to the 4 items in Spybot immunization being removed due to security overlap with Avast. Spybot immunized 4 sites that had Avast mentioned in the link, I'm not sure why but sometimes websites will imitate security programs and actually be another program, (but I can only guess if that is the case here), the Avast program likely may have removed those in an effort to protect itself from malware inserting links in the hosts file to prevent infected users from being able to go to the Avast website. But this is all speculation and guesses, and it's been a few years so if it was that, I have no idea if that applies today. (The spybot users did some nice looking into it when I read through that link again, I must say.)
https://forums.spybot.info/showthrea...y-Immunization

I did a few searches to try to find posts about speeding up the Spybot scan.(I guess a few too many searches because Google made me checkmark that I wasn't a robot.) I couldn't find too much info that wasn't from many years ago and related to a former version.
You could try disabling scanning for usage tracks, that might speed up the Spybot system scan a little bit. If you want to try that, then rightclick Spybot Start Center and select Run As Administrator. If it opens in Overview mode, click Show Details in the lower right corner. Place a checkmark in Advanced User Mode, click Settings, go to the categories tab, somewhere in the window rightclick and select Spyware scan only. That might help, it's worth a try