I'm of the opinion that there is no such thing as a "transition" gun. Until the gun is cleared by Customs and leaves the bonded wharehouse it is in, it's not legally in the US. That's the whole point of storing them in a customs bonded wharehouse. The date they "hit the shores" of the US was when they were released by customs. If that date is after the ban (as evidenced by the neutering of evil features) then it's a post-ban.
Whether it's legal to put evil features back on I don't know. I kinda doubt it, as I remember alot of talk about how it wasnt' legal to modify an import into a gun that was not importable, but who knows?
The law wasn't really well written, nor understood. It would be a simple enough matter to add some US parts now and not worry about it. It sure wouldn't prevent me from buying one at the right price.
Ross