This might explain some things.
Drawing shows audio level if you play a loud beep followed by a softer beep - so the release behavior, with no Knee, in version BETA018.
Top part:
RED is dB style ON - flatter
GREEN is dB style OFF - stronger rise at start, more slowing down at end
Bottom part:
BLUE shows Knee on Target ON
PURPLE line shows Knee on Target OFF
Behavior is shown when the 2nd beep is softer than the threshold level. So the PURPLE line abruptly stops, the BLUE one rises more slowly than normally (dotted lines show the behavior if the 2nd beep had been above threshold level). Abrupt changes are bad, but in case of the blue line the volume rise is different near the threshold which can be annoying and making it configure the behavior properly.
Using Knee helps here (the abrupt end becomes less abrupt) but it still ends very very rapidly, not smooth as the BLUE line does.
For BETA020 the shape is different again (top image), and it behaves as if "Knee on Target" is OFF (abrupt stop, purple line).