No plastic fo me! I like to make them loose fitting too.. So they just fit nice on the string with no snap but no slop side to side. Only broken them due to 'robinhoods' which is really about the only way to break one unintentionally. No problems stacking arrows, no problems filling the freezer, and definitely no issue with them wearing out. Got self nocks with thousands of shots on em that have no wear. You'll break or lose plastic nocks long before you have any issues with a self nock.
There is the convenience factor I suppose. All you gotta do is taper and glue a plastic nock and then glue another if it breaks or pops off. I find making arrows very therapeutic anyway, and a beautifully crafted self nock is my favorite part, so I'll pass on the convenience.
I think you're putting too much thought into it. There are a lot of factors that effect arrow flight but there is no way you're going to notice a micro-measurement of inconsistency in the nocks. As far as I know you should be mostly concerned with weight and spine consistency for accurate shooting. Iv got some nocks that are noticeably different from the next and there is no difference in flight whatsoever. Your fletching does a remarkable job of steering out the silly little stuff.
Arrows were found in Denmark dating 9,000 - 8000 B.C... As early as 16,000 B.C. there is evidence of flints heads attached to split shafts with sinew and fletchings being glued and bound. The first polymer plastic was invented in 1907... That should explain everything