The best way I have found to look at it is ,the fluid in a brake system is sealed and completely filled with fluid and does not compress...............this makes the fluid basically mechanical {like solid linkage}.
Pressure at one end{master cylinder} is going to be exactly the same at the other end{caliper/wheel cylinder} unless rubber lines are exspanding etc.

A giant piece of line in the middle is disregarded in the system ,if,it reduces back down to the small size before entering the caliper/wheel cylinder.....2 inches of fluid travel in a 3/16 th line will only be approx a 1/4 inch travel in 1 inch line,but will regain 2 inches of travel when that volume is reduced back down to 3/16ths......basically the fluid acts like solid linkage while its contained inside the line.
Thats how it was exsplained to me..I dunno?