Early RK will quiet down with some RPM as the pump moves enough Oil to re-establish the Oil wedge between the crank and rod bearing, dropping oil pressure at idle is a handy way to follow the bearing wear as RK gets worse.
Scenario goes, bit of wear pressure drops you lose the wedge and the rod bearing touches the crank (something that should NEVER happen after the first dozen Revolutions in a healthy engine)
When the bearing touches the crank it transfers some bearing material to the crank pin (microscopic at this point) each time it touches it transfers a little more then once revving hard enough for the wedge to return (bearings float on a wedge of oil in use) this material is scoured away leaving a bigger bearing clearance and the drop in idle oil pressure I mentioned earlier.
This is a self fulfilling prophecy as in time you wear enough of the bearing away that it's hitting the crank all the time and you have full blown RK.
This can occur slowly or all in a rush if you run low on oil and stand on the brakes or corner hard enough to uncover the pickup. (this is my reasoning on ALWAYS running +1qt of oil in a 7M and every other engine after I’ve checked that it doesn’t let the crank dip into the oil while running)
As for "lifters" near enough but incorrect "followers" would be closer, I use "buckets" as it's more descriptive for my senile old brain
