The thing about Min OAL is just a safety thing, to never go below that with the listed powder charge or bad things can/will happen.
Never took it as argumentative, just us talking (typing here)
When I first started loading, I used dippers and made a lot of custom ones by grinding down shell casings and gluing on little handles.
It seems for the auto discs the finer powders are a lot closer to the chart then the flake. Powders like Blue Dot, Unique are probably 2-3 discs different in my batches.
I tried the micrometer thing but for small charges it's useless.
I just find a disc that is close to what I really want and live with it. If the max load is 6.0 grs and all I can get is 5.5 it works for me. The paper can't tell.