Clutch losing pressure?

Alright, before I go bleeding the clutch without it needing it, or before I go buying a new master cylinder, if it doesn’t need it…

Here’s some more symptoms that are becoming more consistent.

The clutch, if pressed quickly down, will generate pressure.

If you press the clutch in slowly, you will generate no pressure at all.

I know that pressure loss like that and needed pumping of the clutch is usually an indicator of a bad master.

Does a bad master cylinder ALWAYS coincide with fluid loss? Also, if it was air in the system, how would it get introduced into the system when the fluid level has been kept full all along?