After a couple days to cool down and read through all 230 pages of this thread I've accepted the situation. Seems like people either get approved in the first 4 months or are waiting for a year or more.
My case has been updated both days since the interview, but I dunno how much that really means. As far as the "previous passports" thing all my research has confirmed my opinion that this question is referring to passports with other countries you may hold that have been used to travel. Your Canadian passport has machine readable lettering on the bottom of your bio page that directly refers to any previously expired canadian passport you've ever held, so the US government already has access to your expired passports. It also makes no sense to tell someone to submit a questionnaire that "takes 60 minutes" the same day if they require you to dig up 40+ years of expired passport history. If I'm wrong, I guess I'll find out eventually.
The fact they are giving the DS5535 in concert with missing document requests as well as giving it to kids and babies virtually guarantees it is a (badly) automated procedure outside of the consulates control. I really feel like I was dinged before I even handed my documents over. Just a general intuition I guess. There is absolutely no legitimate reason at all why this was required of me. I am squeaky clean legally, have no suspect history of any kind, have a very uncommon english name that until a few years ago wasn't even Google-able, have only travelled outside north america once, and that was to western europe where I met my wife in 2015. Prior to that my last international travel was a trip to seattle in 2004.
I pray for everyone in this thread on AP due to the DS that their cases will clear asap and without having to sue. After this long a road and so many hiccups in the way, we don't, unfortunately, expect anything but the worst case scenario regarding this and will not be waiting much longer than 90 days before taking legal action. Hopefully it gets approved naturally before then.
I chalk it up to Covid. With all the supply chain issues our societies are experiencing it only makes sense there are major issues with the immigration chain too. It's appalling and frustrating, but "it is what it is." All the best.