The original 'Best Buy' Pre-Order perk was the 'Rivera' Tribble for Federation Officers, and the pet 'Targ' for KDF players. (The Pet Targ still cannot be claimed in the C-Store by Federation Players...)
The only C-Store Tribble that is usable by KDF would be the assimilated 'Tribble of Borg'....
that would be cuz klinks hate tribbles hey see them as an envromental hazard
I would buy that explanation if it was only klingon race characters, but it isn't. Especially since tribbles drop like crazy and I'm fully equipped with other types - only not the type I paid for (with game preorder I think).