You obviously do not understand compressibility and incompressibility.
Obviously I do. Ron
This bit of ignorance begs to differ.
And none of that fluid connects the front and rear systems by hydraulics.
What connects the front and rear piston in the M/C when you step on the brakes in a normally operating split system?
HYDRAULIC FLUID, there is no mechanical connection at this point.
Why does it work that way?
Because hydraulic fluid is incompressible and you get instant action on both.
What happens if you have a leak? Depends on which end but in either case neither one makes and pressure till the piston with the leak side bottoms out mechanically. Degrading your braking. UNLESS, you have someway to pinch off that leak (safety valve). Which lessens the degradation.