Finally it is more compressible than the glycol and ester fluids. This compressibility goes up with temperature.
I concur with most of your other points, but I have "read" the compressibility issue with DOT5 is, it traps/entrains air when pouring, and first impressions just after installing, leads to the compressibility observations, unfairly, if confirmable. The rising temp issue leading to increased compressibility, is the first I have heard of that condition.
A reason for the assertion of compressibility is that if dot 5 container is not handled very gently, that very fine air bubbles can be produced in the fluid that will cause this problem as air is compressible. The key is to not shake the container and if it has been do not use until fluid is again clear. I have no idea how long that might take.
