Logically those cutouts should be filled, however, gaijin modelled the mantlet based off an incomplete picture of the trunnion during production.
Now, unless someone hits those holes, the mantlet can stop 3BM42, which is a really nice change.
(3BM42 has 457mm of pen at 0m)
The entire lower/middle mantlet should be at 450-480mm according to how they’ve modelled it.
Step in the right direction, but I guess work needs to be done