I had the same problem. In my case, it depended on the integration/component.
I recently switched all the hardcoded IPs in my configuration files to local names instead and I saw a huge jump in my pihole chart (like you did). Requests from my hassio went from the low 100s to nearly 3000 per 10 minute timeframe. I could see which host it was requesting records for in the pihole logs (like you did) and I then used trial and error to back out the changes until I found the culprit.
It was ZoneMinder, my security camera integration/component. When I put the hostname of the system in there instead of the IP I get nearly 3000 queries in 10 minutes from hassio for it.
I just barely figured this out you can see the requests dive at the end.
