Its getting complicated.
On a Boeing there are one set of brake cylinders.
On an Airbus there are two sets.
So on a Boeing either left or right (B757) or centre or right (B767) hyds can pressurise the brakes, but there is only one return path.
On the B757 the return is to the right system. So if you turn on the L sys first, it will pressurise the brakes. When you turn off the hyds the fluid will slowly bleed back into the R system. So to avoid hyd transfer on a B757 always pressurise the R sys before the L sys.
Our crews don't, so we have to transfer the fluid back every week by setting the parking brake with the R sys and letting it off with the L sys.
Same can happen on B767 B744 and B777 (but different systems).
On an Airbus the main and alternate brakes have their own set of brake cylinders so it doesn't happen.
Also on an Airbus, when you set the parking brake on a nightstop it is still set in the morning. While on a B757 the accumulator is usually empty.