[KevinH]

When files are moved, especially when css files are moved and images are moved, each css sheet is parsed to look for url(), background images, importing other css files, etc and any that need updated due to the file move. That is true of page maps and templates that link to any files moved. So all of that is expected behaviour given the movement of that file or links into that file or out of that file.

In an unrelated change, I tried to speedup OPF parsing itself to try to speed up adding blank xhtml files. You are probably seeing those slight speedups in your timings as Importing an Epub is only a light user of opf parsing in general. Mainly just the manifest.