I think the general definition of a benchmark ball is one that handles TRUE medium oil with a controlled ball path and a controlled overall ball reaction. It gets TRUE medium length (not long, not early). It has a medium arc-ing (not hockey stick, not skid/flip) breakpoint.
It can polished or matte finished. It can be a resin pearl, a particle pearl, a solid particle or solid resin. That makes no difference.
Your release can determine what ball you need as a benchmark because some releases cause many even balls to be flippy and other releases cause flippy balls to be more even reacting.
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"None are so blind as those who will not see."