There are multiple reasons for the increased amount of differences we've
been seeing lately and for the raise of the threshold:
1. Recent hardening against cache poisoning (CVE-2025-40778) have
uncovered a few edge cases where the domain can't be properly
resolved with the new protections in place, but those are issues with
upstream configuration and DNS setup.
2. The same hardening magnified some behaviour differences between 9.21
and older versions. Some misconfigured domains, which can be resolved
with BIND 9.20 and older are no longer resolvable in 9.21+. This can
be again attributed to upstream DNS misconfiguration. See #5649.
3. A change in the respdiff CI job to include timeouts in the
comparison, or rather, increasing the timeouts to resolve the
previously timed out queries, which are typically failures. With the
previous job configuration, those were omitted from comparison,
because they were timeouts. Now, there should be no timeouts, but
there is a slight increase in the amount of differences for the
threshold evaluation.
(cherry picked from commit
bcc4369b0bf243433ca5334cdce3982a15ce4027)