Roof insulation with vapor barrier - counter battens & insulation

Hello, I have already read quite a bit here, but I have not found the right answer or a definitive response to my question.
I have the following roof structure
Roof tiles, underlay membrane, 160mm insulation between rafters, WLG032, vapor barrier
Now my question is whether it is necessarily required to place an additional insulation layer between the counter battens and the drywall sheets or if it is not necessary.

Kind regards and many thanks in advance

unnecessary.

This obscures the "better" heat transfer of the rafters. It is not really necessary, but with a sparse 160mm insulation it cannot hurt either.

Exactly, unnecessary but not completely pointless. I can't calculate that, but here is someone who can. Maybe he will speak up. K.

There is the U-value calculator (ubakus) available online, which is freely accessible.

With 16cm WLG 032, the additional 3cm between counter and load-bearing battens are even necessary to comply with the Energy Saving Ordinance (U-value = 0.24). With only 16cm, you get 0.25, with the additional 3cm WLG 035, you end up at 0.21.

You don't have to, but you can; most of the time it also makes sense. However, it would be nonsense to add even more insulation inside the vapor barrier.