The one with the boxes has been listed as the A2G one.
The problem with a "gunsight" for WGr 21s is that it won't ever aim true in 99% of cases. Every thing from your pitch up/down, your airspeed when releasing, the target's orientation, angle, speed, etc, will ALL affect how and where the rockets fly.
From a dead level, even speed, if you match the target's speed and alt precisely with no deviation in your course, it will be about 1.4k to target. However, I've lobbed them at about every angle you can imagine. You dive on a target and your rockets will got further because they have your kinetic energy behind them. You climb up at a target and they won't go as far because they are starting from a slower speed.
I've had lancs flying past me, been way too low and out of position in a 190A, lobbed a rocket almost on-the-pipper for my gunsight, and saw the fluffy puffs and got the kills. Other times I've had to nose up so high I'm firing blind at targets well under my nose and still hit.
No gunsight you could draw on a bitmap would have helped me in either case.