Small update. Since I was assured the battery was not fake, I decided to test it a bit before sending it back for a replacement. I was ready to ask for a 40T, mind you. As I had said, the battery seemed to be performing poorly, not hitting as hard as the 40T at decreased charge. By 50% it was weak. Usable, but noticeably lacking in power (all testing was done with the Zeus X with a A1 NexMesh 0.13Ω at 70W). Thing is, the 40T seemed to me like it was performing better under similar circumstances, but the charge would drop off a cliff quickly under 60-70%. Also, when charging the 40T from completely empty to 100%, the charger would show about 3400mAh charged. Well, thing is, the damn Molicel just wouldn't die. I was chain vaping for hours and hours with less than 50% battery left, the performance had dropped quite a bit (which at first led me to believe it was actually fake) but it kept going on and on. It finally died at some point, WAY later than I had expected, so I left it to charge overnight. Same charger, same mod, the Molicel topped up with 3930mAh. 3930! Unbelievable! After I took it out of the charger, I put it in my mod and it immediately fired great, hitting obviously harder than the full 40T. Soooo... Yeah, not fake, it's either faulty or it has to do with manufacturing tolerances. So I emailed the shop and asked for another Molicel. Let's hope this works out for me. The bright side to all of this is that a) now I know the Molicel is actually the best battery if you can fit it in your mod and b) the shop is actually great and exceeded my expectations, so they won me back as a customer.
I feel like I haven't said it enough times already, so I'll say it again. Thank you everyone for taking the time to help, each in their own way, be it analysis of the battery or calling me fucking stupid like I deserved.