I think another interesting question here is why Slack bothered in the first place. As was pointed out on the other DNSSEC thread today: practically nobody in the technology industry uses DNSSEC in the first place. Presumably, Slack did DNSSEC (they don't anymore!) in service of FedRAMP compliance. Why? Slack has one of the most popular products in all of computing. What bad thing was going to happen if they said "nah, we're going to go with Cloud.gov's recommendation and not this FedRAMP document"?