I asked them re: a Rebel and they would only do a replacement bolt if they had the action in hand to ensure fit. I would expect that to be their answer even on the Anti-X because of concern about the lugs, headspace isn't the only dimension at play in the action. The Anti X would make barrel changes easier though, pairing with the shouldered pre-fit options some barrel makers are starting to offer.
I'm aware. An individual bolt still has to be lapped to fit into the lug recesses to maintain that tolerance. There are also more dimensions in an action at play than simply headspace. Timing is another area where fitment could need to be adjusted, regardless of how well the bolt itself is machined.
I loaned out a Defiance Deviant bolt out at a PRS match a while back. The person ended up not using it (probably a good thing). The thought at the time was a Deviant bolt for a different Deviant action seemed right at the time. Now thinking back on it, things could have gone wrong. We may have gotten lucky on that idea! LOL!