Spading tank lines doesn't give bonus to heli research

I’m using my 8.7 lineup in Russia to research Helis now that I have everything done in ground forces. I’ve noticed that finishing a line in modifications does not allow for bonus RP towards Helis. Is this intentional? Why allow for heli research if I cannot use bonus rp towards unlocking more vehicles.

The feature is still kind of WIP
Maybe submit a bug report I’m not sure