Can you please upload a firmware to test the new low setting?
Any form of artificially generated scanlines will result in visible gamma change on a display that is calibrated to a gamma of 2.2 with SOLID (full, no holes) greyscale.
Yes, that implies that removing half the visible area of a certain grey shade will make it visibly darker.
The human eye is FAR from linear therefor using 100% strength scanlines will NOT result in the same visible gamma curve as without scanlines on the same monitor even though same amount of area was removed from each shade of grey.
Hybrid scanlines kills two birds with one stone in this instance, it will emulated the larger beam spot with brighter shades AND fix the visible gamma curve,,, IF properly adjusted.
If the resulting curve is darker looking at the darker shades (which it will because hybrid scanlines [and standard] do not touch this region of the grey scale), you can always bring the brightness slightly up on your TV or lower the Gamma setting if it has one.
I don’t think the two completely different equations of scanline can be combined in any simple way.
As said, just bring the brightness on your TV up to brighten the resulting dark region, or lower the gamma.