I kind of agree though. Is a retailer just gonna rush through the job to get as many guns downgraded as quickly as possible? Is that retailer even qualified to do the job? (I can think of at least one retailer I wouldn't want touching my mechbox).
It's the host's responsibility to chrony guns, specially of new people who are an unknown factor and are potentially fielding a stock chinese gun shooting over 400.
And it's the owners' responsibility to either downgrade their gun, find a friend to do it for them or take it to a qualified gundoc to get it done.
But I don't think that's a burden the retailer/importer should carry, specially if he's going to charge more for it (maybe he's paying for a qualified tech to get the job done properly/professionally) and some other retailer will just offer stuff for that much cheaper and not downgrade -- the hot guns will still be on the market and that other retailer just gets screwed in the end for offering the downgrade. Worst case maybe offer it as an option.