Well... the problem being solved is like... well, there's two methods to calculate speed, one based on Rotation, and it's literally something like, Degrees per tick, so if the inserter only needs to move 90 degrees instead of 180 degrees, it'll be twice as fast and there's nothing you can do about it.
Alternatively there's extension speed, and I'm not 100% sure how that works, but it's the opposite to rotation, how fast does the arm extend outwards from, or in towards the base of the inserter. Again, it's a speed, distance/angle per tick, and if the destination is twice the distance, it'll take twice as long, there's really nothing you can do to change that.
So... I know how it works, but, there's really not any "Fix" for it.