The overall shape of the seat post is ever so slightly different. The area where the seat tube meets the top tube is also marginally off.
While the bonding of the BSA bottom bracket to the X68 frame is rough compared to the SL8, it's on par with $500 frames. Specialized does a superb job of facing the bottom bracket (and caliper mounts), and you can clearly see how smooth the bare carbon is around the BB. I have a video on this. However, I can't tell in TanTan's photos if they either faced the BB then added matte black paint or simply not face it at all.
Personally I don't believe the X68 will catastrophically explode like one would expect if this was a purely counterfeit frame sold on AliExpress. That would be a bad look for a genuine supplier like TanTan. And other than TanTan using that seatpost gripping material, the frame would 99% pass the eye test for a genuine SL8.