The problem is there is no detailed information on just what that is.
Personally I'm not overly concerned with that as the whole point of a resident AV is to prevent the infection in the first place, so assuming that you were clean when you shutdown it shouldn't be an issue on startup. But I still don't feel avast starts so late as not to be able to stop before execution.
The bigger problem really is if it wasn't detected in the first place for it to be able to run on startup, so if it wasn't before I don't see it getting detected later. And there is no mention if this/these malware samples are/were detected to start of with.
I have been using avast for nine years and not had a single infection.