I baseline understand the complaint here - it feels weird to tack on a penalty that effectively negates Rank 6
What I don't understand is... how much of a problem is it in gameplay? On paper, I agree that this is a pointless negative. It makes no sense to negate the R6 for a minor benefit. But how often are you actually aiming with the scope for railjack? Battle Avionics spam aside, I find it much easier to follow the lead indicators on fighters without scoping in at all.
My complaint for Gunnery R10 is more to the point that it doesn't feel worthwhile of being a max rank unlock. It feels like something that would have been useful around R4 for players still learning the ropes on how this game mode works. It's nowhere near the scale of the Void Radiance (Madurai) of problematic design. It's more like Lightning Dash (Zenurik): Sure, you could technically turn it on and use it... but why would you?