Bo Katan Mandalore datacron bonus turn not applying correctly

DTMG causes enemies to lose tm whenever they gain bonus turns. So this is one thing going on. I think they're was also some issue where his allies gain as much tm as enemies lose that wasn't written down in the description or something. Or it could be the reverse.

Also, his kit reveal says Imperial Remnant allies gain 100% tm when another ally is defeated, as opposed to just Moff Gideon like it reads in the game description. The mechanics seem to match. So Imperial Remnant probably gained 100% tm, and Bo was reduced to 90%.

The 10% tm removal still leaves her with an effective speed of over 2,000, so there still has to be something else going on that caused the enemy to get tm when nothing stated in game via abilities or datacrons would give them tm.

If what you're saying is true, that the original preview description and possibly the programming gives all remnant allies 100% tm when an ally is defeated, then that's a bug because the description in game says only dtmg gains 100% tm when another ally is defeated. 

Whatever the actual cause, something didn't function as written.

Right, I think it could be the latter, because you're right that the 10% is probably not enough (or effective 20%, since she would have had two bonus turns).

But I suspect it could be shennanigans with DTMG's kit not working as written (as has been reported before) rather than something wrong with the datacron.