IMHO this PI should be honoring the same (tweakable) setting as the normal Get Metadata feature to avoid betting all Calibre usage black listed.
Why the friggan rush? You did not have page counts before. It took you quite a bit of time to accumulate hundreds of books. Believe me, I know! One of the first things I did with Calibre was enter my Paper Library (~900 paperbacks).
Many were so old, their (actual) covers were not available for download (or the quality was distorted). Batches of 10-20, correct obvious Author-Title errors-research Not Found (some were pre-ISBN), Slap the book on the Flatbed Scanner when needed, then add that.
Repeat until my back gave out and call it a day.
Later I would gather missing metadata for small batches.
Total time, working a couple of hours a whack: over a year. And note: that metadata had not been really cleaned (42 versions of Science Fiction). Sometimes I would have to retrieve the copy and review because the tag said "SF&F" but I did not remember any F (or the flip)
Take your time. Do the books NOW, that you plan to read in the near future. If you are like me, you will adjust what or how you file books in your library (hoo-boy, some adjustments affected lots of books ).