I have flagged this as ridiculous clickbait. "I added a notification email to people who didn't finish signing up and made some extra money" is the gist of the article, and much more mundane.
"How I made 10% of my side project's incomes with a bot written in 4 hours"... "then decreased my products lifetime earning by 15% permanently".<p>Now that it's publicly known, why would anyone sign-up immediately? Surely this addition has now done more harm?
It could also be that some or all of these 10% knew or expected that they would get a discount if they did this, in which case it would be a loss of (max) 1.5%.