This firearm attachment's purpose is unclear

The only possibilities I can think of are that they might release the AN-94 or the M16A4 in the future. However, based on the attachment description, the two-round and three-round burst modes don't seem to be useful. Because Burst Mode not Semi-automatic Mode.

AK4D(G3A3)?Compared to bf3, the G3A3 in bf6 has significantly reduced recoil and much tighter bullet spread. No need to use semi-auto mode.

 but,one thing is certain: there are too few guns use 5.45x39mm ammo, TTK is unremarkable.too bad!

We need more weapons that use 5.45x39mm ammo,  the AK series, and the perennial Battlefield favorite, the AN-94 (from the early Bad Company 2 to Battlefield 3, Battlefield 4, and now Battlefield 2042).

I genuinely hope that classic weapons from Bad Company 2, Battlefield 3, and Battlefield 4 could all make a return in the next Battlefield 6.( such as ACWR,SKS,PKP,ASVAL)