Google announced the other day that starting on April 12, 2020 it began tracking fewer pages for its reporting engine. Specifically for the AMP, Mobile Usability, Speed, all rich result reports. This was done to improve performance of the reporting system. But tracking fewer pages can result in some issues.
Google said "these reports have been changed to cover a smaller number of pages, in order to provide better performance in Search Console." The result is that "you might see a decrease in the number of items and pages tracked in these reports."
Of course, with any change to reporting in Search Console, this "does not affect Search results, only the data reporting in Search Console," as Google said.
So if you see a change in the number of items being reported in Search Console on or after April 12th, this is why.
Forum discussion at Twitter.
