line lock orientation

That chamber is also full of brake fluid,which is....... in-compressible.
But the compensating port is at the rearmost part of that chamber. As soon as the rearmost piston covers the port, the fluid moves out to the front calipers. If the caliper pistons are in close proximity to the discs, requiring a minimum amount of fluid to do their thing, then it should work.
But if seal retraction or knock-back is excessive, or you have huge calipers or with multiple pistons, and or you are using a tiny m/c;then that rearmost piston may travel forward and hit the stop on the frontmost piston, and then everything will lock up solid. This may occur before there is sufficient fluid pressure in the front brake system, to hold the car on the line;
IDK.
I tried something like this on my car once, and it didn't work on the KH 4 pistons with a 7/8 M/C.
Perhaps it would have, with a bigger M/C, or if I had shortened the mechanical stop. Or tightened up the bearings. That was a long time ago.

TB
I assume your arrow at "because of this" is pointing to the mechanical stop, and not to the piston return spring.