That doesn’t sound unreasonable, I thought the figure was far more for a typical ‘60s-80s pop album per stamper (>4k). Classical far less, but it was a far smaller market too.
The thing I was trying to figure out is whether these comparatively high pressing number Blue Notes were all coming off one machine at the pressing plant, or whether they were kitting out more than one machine to get the order complete in half the time. If the latter it may help explain the differences in quality being reported.
As an example back in the heyday of vinyl it was commonplace for multiple pressing plants to work on a given title to get it into the shops on the arranged release date. Things are obviously far smaller now, but it wouldn’t surprise me if a couple of machines at the plant were producing these, and maybe one isn’t as well setup as the other.