No confirmation. AFAIK it was just an educated guess. For all we know, Epi could be making their own, in-house.
There could be other factories winding them.
My experience in China:
If somebody is making ANYTHING and appears to be profitable others will attempt the same thing, with varying success and quality. Some of the copies can be pretty hilarious, some better than the originals.
Thunderbird style covers, bobbins, and magnets are now easy to source. Bottom plates are very low tech.
Once the latest Epi TBirds come on the market, there will be others making similar pickups in China. My guess is it's already happening.
CAVEAT EMPTOR, as always!