Why does increased traffic happen during Site Audit Crawls with Core Web Vitals enabled?
When Core Web Vitals are enabled, each page being crawled in a Site Audit crawl will also call the Pagespeed Insights API, as long as it's allowed to be crawled.
Each time that API is called, Google opens the URL mentioned in the API request in their "headless browser" (The same way Ahrefs SiteAuditBot crawls any page). Each request then gets registered in Google Analytics as 1 visit to that page.
As a result, this additional traffic gets registered by Google Analytics.
How to filter out the additional traffic related to CWV in Google Analytics
Normally this shouldn't happen if the ‘Exclude all hits from known bots and spiders’ view setting is enabled in your Google Analytics view.
However this seems to be a known issue at Google, and they are working on a fix.
In the meantime, you can filter out traffic from Google by creating an Exclude filter with Campaign Source selected, and enter
developers.google\.com in the Filter Pattern field.
If that doesn't work, you can also try another filter with IP Address selected, and enter
^66\.249\.(6[4–9]|[7–8][0–9]|9[0–5])\.([0–9]|[1–9][0–9]|1([0–9][0–9])|2([0–4][0–9]|5[0–5]))$ in the Filter Pattern field.