Slant 6 pcv valve rattling issue

I'll throw out a few semi-formed thoughts:
1. There are many different PN's for PCV valves, but wonder how much they really differ. If it fits in the grommet hole and has a correct size hose nipple, it "should work". Consider that even for the same engine, the blow-by and thus PCV flow varies considerably over its life.
2. Even among classic Mopar's, the PCV valves differed. My 65 SB & BB used one w/ metal thread & nut which screwed into a metal cap which fit over a "stove-pipe" on the valve cover, and yes they were smart enough to put the nut on the outside. I recall my 64 slant is different PN which pops in a rubber grommet, as shown above, but the valve cover has just 1 grommet (update, just looked and my 64 slant has the same metal PCV valve in "stove-pipe"). The breather is in the oil fill cap. But, some of this might be specific to a CA "Clean Air Package".
3. Whenever searching for a vacuum leak, suspect the PCV valve. Similar to a brake booster, it is a large hose plumbed straight to intake manifold vacuum. I think the way it is supposed to work is that the valve is forced closed when there is a high dP across the valve. The intent is that it is closed when idling (high vacuum), so it doesn't mess up the O/F ratio. There is a small designed-in leak when closed. At high throttle (dP drops), a spring opens it to vent crankcase fumes into the intake. At these higher air flows, the fumes don't mess up the O/F. That is why old mechanics would test one by popping it off with the engine idling, then put their thumb over the end to feel it click open as inlet vacuum builds (dP drops).
4. Given above, if you have a lot of blow-by at idle, seems the PCV valve would just close off even tighter (greater dP). Therefore, my suggestion that blowby might make it rattle at idle sounds unlikely. On the downside, the crankcase might pressurize even more, which exacerbates oil leaks. Engines before PCV simply vented the crankcase to atmosphere, so no pressure built up. Nicer to capture and burn them. The fumes don't gunk up the intake because the gas keeps it clean. But PCV has always helped gunk up diesel intakes, and similar has been seen in the new "direct injection" gas engines, some of which require the intake to be removed and degunked every 50,000 miles.