Thanks Charles, the split tubes are fully seated in the inner knobs.
There's a section that T's off of the tube to prevent spinning and they're seated down in there.
I can physically see a different length of split tube from the tip of the tube to where the T section begins on one set of knobs vs the other.
I took the smooth end of a 9/64" bit and slid it down each brass potentiometer shaft, marking with tape, I found them both to have the same depth.
The longer inner knobs exceed the available depth, but the shorter ones are equal so those are the ones I'll use.
Next problem, one of the shorter knobs has a mangled split tube so I need to replace it.
Thanks Andrew, that is your picture I poached.
I've seen the picture from time to time, but it's just a relist then, and not multiple examples.
Glad there's consensus on the knob sets being common to all 3 varieties by a given manufacturer.