Optipower Ultra 6s 5000mah 50C "optimized"?

[Rc-Heaven]

Received a bunch of new packs a few days ago and noticed a couple of the 6s 5000 50C was smaller than the other new 6s 5000 50C and my older units. So I contacted Tony at experience rc and he said they'd next-day out all matching sets, which they did (Fantastic service)! To my surprise all of the packs re-sent to me was of this smaller form factor; same length and width of the older packs but they weren't as thick (44mm compared to 55mm). I also noticed they've got serial numbers now as well, haven't thrown them on a scale but weight feels about the same. Anyone else seeing this yet?
I was assured they are 5000mah 50C, and the eos sentry confirms 6 evenly matched cells. I was told to solder them up and charge and fly. Of course I can verify capacity at the charge cycle, bit it's not going to readily apparent if the discharge rate is what is supposed to be. Nonetheless the guys there said they'd take care of me if I'm not happy and I'm really more curious about the size difference rather than the worried about integrity of the packs, I've gotten nothing but excellent service, so I'll just fly them and see.