[knot-dns-users] Don't preserve CD flag?

I'm an engineer at Dyn and I work on the same team as Matthijs Mekking. I noticed that commit 3f950e1d ( https://gitlab.labs.nic.cz/labs/knot/commit/3f950e1d3f323b0ebbd339de29f8c8b…) changes the handling of the CD bit in responses. The test code comments indicate that this is in accordance with https://tools.ietf.org/html/rfc4035#section-3.1.6, but my reading is that it contradicts section 3 of the same RFC. I was wondering if somebody could explain the history or the thinking behind this change. Thanks in advance! John-Paul Gignac