Fatality says it only works with BS Attacks that use BS Attribute. Do direct template weapons use BS Attribute?
That's honestly what I imagine it is, in a lot of cases - like the Druze are using custom caliber weaponry with extra stopping power and so on. That's definitely why TAGs get the bonus.
Funny thing is the level 2 with the extra crits winning the FtF works more like an aimbot than like bigger bullets. Love this GIF for FAT2 XD