I call bullshit. I searched "entry level developer" on indeed and spot checked 10 of them. Not one said 3 years experience required.
As other posters have pointed out, did the ads say 3 years’ experience in a similar job - or 3 years’ experience with a particular language, framework or platform? Even if someone has a Bachelors in CS, I wouldn’t hire for an entry-level C++ gif without 3 years’ experience with the language: I expect them to pick it up during their time in academia - especially as many (of the best) start coding in high-school or ear…
Which speaking as an aside; I was denied an internship back in college because I didn't have three years of professional experience in Java. Needless to say I found it absurd at the time.
You also assume that the best people are coding earlier or have the ability to code earlier. Some of the best developers I've worked with didn't start coding until later in their life.