To give another update, when I called into the call center they asked me to email their audit department at
[email protected] (sharing this here since Air France already discloses it on their website and it's been shared on FT before).
Hot take: the perception of what's fair use of the Flying Blue program differs on if you're based in Europe or in the US. If you're based out of France/Amsterdam, of course it's easy to point at victims of these audits and blame them for not having flown a single paid mile with Air France/KLM. But if you're based out of US and flying mostly domestic flights on SkyTeam, rationally the most obvious airline to credit to is the home airline, Delta, even if you have the option of transferring points to Flying Blue. Becoming a "spending programme" where they get many US-based customers only using them for award travel is Flying Blue's own doing - y'all have to understand that Flying Blue is partners with literally every major US-based bank - Amex, Chase, Citi, Bilt, Capital One - and with banks encouraging transfers to these programs (for instance, through point.me which is now free for Amex/Bilt) it should have been no surprise to the Flying Blue partnership team that wouldn't only reach revenue customers. Flying Blue entered the US market because it's huge and lucrative, but they can't have their cake and eat it too - so limiting award booking under the pretense of fraud would be a disingenuous way of entering the partnership.
I'm of the opinion that Flying Blue is in general trying to do the right thing - but they've been (1) burned by accounts getting hacked and unauthorized spending of miles resulting in losses and (2) mileage brokers farming points from people wanting to liquidate points for cash and booking lucrative redemptions (which diminishes inventory for customers who actually use the FF program directly). It just sucks that they're not able to accurately distinguish these from legitimate customers trying to book family trips (and yes, users transferring in points are still customers, even if less profitable ones - plus many FF users are terrible at finding good redemptions). In the end, it comes down to bad actors out there - hackers and mileage brokers - and "this is why we can't have nice things."
Edit: got this resolved - support helped me make a new reservation that didn’t get canceled.