...No compromise for safety is happening. The Latch system is designed to take 'forces' from all moments of movement, not just one. Thats how accidents happen, randomly and at all different angles, therefore the Latch system must provide for those.
...l
You're missing my point. When the child seat is correctly installed, the latch anchors and seat fasteners are colinear, and perpendicular to the mounting plate, which is roughly 45 degrees off horizontal. Regardless of the angle of impact in an accident, the child seat can't move up or down because doing so would compress the seat cushion or seat back. It is effectively "secured" but with a measure of compliance to allow the seat cushions to absorb the "forces". What you did by removing the cushion is remove half the load dampening capabilities of the system and change the angle of the fasteners so that the seat can now move up much further before pushing against the seat back.
Here's a picture of one of the anchors: see how its angled so that correct installation results in the hoop and seat strap being parallel? If you removed the lower cushion in the car pictured, the safe working load would be substantially decreased in any (and every) accident situation in which the brackets are needed.