The only thing I can think of is that since you have both pihole and 1.1.1.1 in the resolv.conf.auto, both will be queried and if you are blocking 1.1.1.1 you won't get an answer.
Resolving an AAAA or IPv6 PTR is not affected by the connection used. You can connect to the NS by IPv4 or IPv6, the result will be the same.
Sorry for my late reply. I have since removed 1.1.1.1 from resolv.conf.auto (which I am not blocking by the way) but the problem persists. DNS resolving is very slow and the log keeps getting riddled.
Enable verbose logging for dnsmasq or run a tcpdump to check what are all these logs about.
150 concurrent requests are way too much.