I did not do Olympiads, but I did score highly in math modeling competitions and won a competitive PhD fellowship. I have had the exact same experience. I will

I did not do Olympiads, but I did score highly in math modeling competitions and won a competitive PhD fellowship. I have had the exact same experience. I will get comments like, "That's the best submission we've seen for that take-home test" followed by literally no response of any kind after that. I've had places say, "you are absolutely perfect for our needs on Team X and you will help us meet our deadlines by the end of the year" and then make a job offer with a salary less than 80% of my current salary, worse equity, and worse benefits. Companies sometimes want on-paper credential, but they almost never care about actual productivity or talent.