The way the OP described it, there is technically nothing wrong with how he's running his AV's (two of them).
The user stated he is only using one in real-time which is the only correct way to use two AV's; he is then using the other as a backup scanner. The only thing he may want to consider is making sure real-time protection on Avast is turned off when he runs an AVG scan and also ensure no AVG services are starting.
The using two AV argument is applicable when you try to have two competing AV's in real-time on your system simultaneously, but you can certainly run manual scans as long as other steps are observed.
What AVG is detecting is software updater which for all practical purposes is nothing more than an add-on, and potentially classified as a PUP by some other companies, and pure useless nonsense as classified by me.
Keeping all the above in mind, no it is most likely not infected, but when running two AV's in this manner, keep in mind that questionable things such as what you encountered may arise when it looks at the other AV's folders but most likely is not a problem.
IMO a better solution is to run Malwarebytes if you're not already and as an additional scanner use Emsisoft Emergency Kit (award winning and much better comparative results than AVG). It's portable which means absolutely nothing is installed. I've been running it for years alongside Avast with no problems.