The buried lede here seems to be that this is yet another serious outage (indirectly) caused by using DNSSEC, though I understand why they don’t emphasize this part, given their strong advocacy for DNSSEC adoption.
Having had to troubleshoot a third-party service not so dissimilar to 1.1.1.1 and prove to them that their infrastructure was misbehaving in a similar manner, I'll take the error thank you.
I don't know why Cloudflare, like Amazon, often get a free-pass on HN for their DNS implementation bugs. Regardless of DNSSEC's merits or otherwise, this bug isn't inherent to DNSSEC.