pihole01 has the address 192.168.1.252
pihole02 has the address 192.168.1.253
both have cloudflared on port 5053
pihole01 in custom dns has 127.0.0.1 # 5053 and 192.168.1.253 # 53
pihole02 in custom dns has only 127.0.0.1 # 5053
in ddwrt I have set two dns 192.168.1.252 and 192.168.1.253
in addition, dhcp-option = 6, 192.168.1.252, 192.168.1.253
each device in the network has two dns 192.168.1.252 and 192.168.1.253 entered
I see that pihole01 uses pihole02 for dns queries but all blocking is in pihole01, pihole02 has a lot of dns queries but nothing blocks
There isn't a right and wrong with these setups. I prefer keeping the two parallel Pi-Holes completely separate. There is no benefit to having one Pi-Hole as the upstream server of the other. The reason all the blocking is done by Pi-Hole-1 is that any DNS requests to that Pi-Hole have to clear the gravity list on that Pi-Hole. Only if the query is not blocked will the query go to Pi-Hole-2, and if they have the same blocklists it won't be blocked on Pi-Hole-2 either.
I would set them both up the same (blocklists, upstream servers, etc.). Then have the router send out the DNS of both Pi-Holes to clients.
To do this, the only change you would need to make to your Pi-Hole-1 is to remove the other Pi-Hole as upstream DNS.