A personal anecdote.
A few months ago, I noticed a huge drop (30%) in my site traffic. The traffic remained low from that point on. Thinking about what might have caused this drop, I looked at my site's git logs, sitemaps, etc. Then I noticed that the traffic saw that sudden dip right around 36 hours after I had run "fetch as google" on a URL many times.
36 hours earlier:
I was used to running "fetch as google" religiously after every article I published. I would then check google to ensure the article is indexed. But that one day, Google just wouldn't index my URL. Also, there was no news of any algorithm change by Google (per Mozcast, SEMrush etc.). Assuming it was a glitch, I ran fetch as google a few more times. Still, no luck.
Wondering if Google crawler Gods thought my article is not unique or valuable enough, I edited the article to make it lengthy and "more unique." Then I did fetch as google a couple more times. Still, Google just wouldn't index the page.
My stubbornness didn't get my anything, and I began to think by running fetch as google too many times, my site got flagged or something. I still have to check about this with search engine experts like Rand Fishkin(MOZ), Neil Patel etc. The cynicism that followed could be entirely in my head only, but ever since that point, I have been very careful about using fetch as google.
I am a changed man.