The funniest part is when an apple/big tech recruiter contacts you, you get to explain your app's design choices during the interview process, they don't hire you and launch that competitor of yours.
I'm sure that there have been times when someone mentioned design / arch / marketing strategies in an interview and later saw the same thing implemented, but I mean have have had multiple times in my life where I told nobody an idea and still saw it implemented somewhere else. Ideas are not half as unique as people like to think they are.