It isn't a "myth" about WRs. The third year is the year where the most WRs do break out. Only, it isn't the ONLY year. Some rookies have great years, though not many. Some second year WRs, though less than third year. Years two and three together account for the lion's share of WR break out years. Year four still have a reasonable amount, but significantly less. And by year five, the odds are pretty high. Is that a myth? I don't think so. But it isn't a "law" either. There is a range and third year is the peak of that range.TEs? I have never seen the statistical analysis, but I doubt if it would be true of them. First of all, there are fewer fantasy relevent TEs and even fewer of them ever become consistent studs. TEs tend to develop pretty late in general.