I think that’s what needs to be done - especially if you suspect the cartridges are inconsistently built (and/or tuned..).
I get the impression from watching their youtube video interview, that they’re sort of “winging it” - but you need to remember, Koetsu cartridges are hand-made too, as other high-end brands probably are.. Maybe some of you have multiples of one model that all sound a little different(?).
Sadly, I can’t afford several Koetsu Jade or Miyajima Madake models for comparison...! Sort of thinking they may be different from each other, depending on build date, or possibly which helper(s) was in the shop that day.
That said, I do like the sound of my Opus3 and intend to buy another.. Opus3 sounds good to me, for the price, especially.
Duane