iterate: more queries than required, in some cases
Example, without dnssec for simplicity:
[plan] plan 'git.nic.cz.' type 'A'
[resl] => using root hints
[resl] => querying: '2001:dc3::35' score: 10 zone cut: '.' m12n: 'Cz.' type: 'NS' proto: 'udp'
[iter] <= using glue for 'c.ns.nic.cz.'
[iter] <= using glue for 'b.ns.nic.cz.'
[iter] <= using glue for 'd.ns.nic.cz.'
[iter] <= using glue for 'a.ns.nic.cz.'
[iter] <= referral response, follow
[resl] <= server: '2001:dc3::35' rtt: 31 ms
[resl] => querying: '2001:678:1::1' score: 10 zone cut: 'cz.' m12n: 'niC.cz.' type: 'NS' proto: 'udp'
[iter] <= rcode: NOERROR
[iter] <= found cut, retrying with non-minimized name
[resl] <= server: '2001:678:1::1' rtt: 4 ms
[resl] => querying: '2001:678:11::1' score: 10 zone cut: 'cz.' m12n: 'gIt.niC.cz.' type: 'A' proto: 'udp'
[iter] <= using glue for 'a.ns.nic.cz.'
[iter] <= using glue for 'b.ns.nic.cz.'
[iter] <= using glue for 'd.ns.nic.cz.'
[iter] <= referral response, follow
[resl] <= server: '2001:678:11::1' rtt: 14 ms
[resl] => querying: '2001:678:10::1' score: 10 zone cut: 'nic.cz.' m12n: 'gIt.nic.cZ.' type: 'A' proto: 'udp'
[iter] <= using glue for 'a.ns.nic.cz.'
[iter] <= using glue for 'b.ns.nic.cz.'
[iter] <= using glue for 'd.ns.nic.cz.'
[iter] <= rcode: NOERROR
[resl] <= server: '2001:678:10::1' rtt: 35 ms
[resl] finished: 4, queries: 1, mempool: 16400 B
It seems an infrequent edge case. AFAIK doing the same (sub-)query twice brings no benefit. (It happens the same with dnssec enabled, only there's lots of additional "noise".)