Here's a question for you

[hvaclogic]

Suppose I'm checking the charge on a system that is running and I realize
that there was refrigerant oil trapped in the hoses. What effect would this have on the readings I'm seeing? No difference? A higher or lower pressure
reading? Just wondering.

[dngtig]

Probably no differance at all. Unless you poured the oil into the hoses. Normal everyday use no differance.

[beenthere]

Make a mess when you disconnect them.

Readings should still be correct. bigger concern is if you had them on a burned out system, did the oil have acid in it.