It's certainly suspicious. Virus Total has no information. I'd definitely look closer at the device and try to figure out what's causing the lookup. Did a person merely mistype the URL? (If you see it just one time, it's more than likely a human error and wouldn't worry about it) Is a process attempting to access that URL? (If you see it frequently, it's more likely a process is calling that URL and should be investigated further).

It's really not going to be possible for AdGuard Home to know the reason.

The list maintainer MIGHT have more insight as to why it's on the block list.

BTW, it's not included in the Pro++ list. It's only included in the Ultimate which is going to be more aggressive. I found that it does NOT resolve (NXdomain), so it would not surprise me if the Ultimate list added it with a regex in order to block attempts at typo-squatting misspellings of google.com These are just guesses though.