Google has posted a warning in the Google Search Console data anomalies page that you can expect those reports to see an increase in the number of issues and affected items and/or pages starting on April 3, 2019. The reason is Google has started to collect data from more pages than it previously did.
The announcement. “April 3, 2019: For most enhancement reports, data is now being collected from more pages than previously reported. Because of this, you might see an increase in issues and affected items/pages on these reports,” Google wrote.
What it means. Google is trying to give SEOs, webmasters, developers and site owners a heads up that if they see increases in the number of issues and affected items or pages reported in these reports, that should be expected. Since it has expanded the number of pages it is looking at, potentially you will see a spike in errors starting on April 3rd.
Which reports are impacted? Google said this affects “most” of the enhancement reports, which can include reports such as the AMP report, mobile usability, products, jobs and others. Google didn’t say which enhancement reports will not be impacted.
Why it matters. If you see new errors, you can assume that those errors have been there previously. Now that Google is reviewing more pages and reporting on issues on those new pages, you can address those issues. These are not necessarily new issues but ones Google had not previously been surfacing based on the pages it reviewed.