I bought a similar looking Alpha SV from eBay - really don't know what to make of it. I have owned various Arcteryx gear of the years and am very familiar with the quality. Careful inspection of this jacket looks flawless - the quality really is what you would expect from Arcteryx down to the smallest details - top notch stitching, YKK powder coated and color matched, Arcteryx detailing of zip pulls, Recco is also present of arm. There are just a few red flags however - the inside label states size S/S instead of the usual S/P for men's size Small and it came with a tag stating Paclite Plus which it obvious is not and certainly looks and feels like the genuine Goretex Pro. My guess from the exacting quality of this jacket indicates it must have originated from an authentic Arcteryx production facility in China but was produced off the books so to speak. There seems to be a lot of this going on judging by what I've been reading on other forums. Too late to send the jacket back and haven't worn it outside yet but will be interesting to see how it holds up when I get round to testing it.
if it's such a good fake you can't tell, does it matter unless you're trying to resell? most of these jackets that are fake are made to the same specs, arcteryx just wants to gatekeep their gear. there really is no difference between a perfect fake and a real one. i have one of each and you really can't tell the difference in real world conditions. there are definitely different levels of fakes. for what it's worth, yes it's fake