I've seen this work the other way too.  Our league started in 1961.  For the 1962 draft, there were a couple of players, most notably Claude Osteen, who were not rookies but were on the availables list because they did not have WIS-eligible seasons in '61.

Several owners - I'm guessing here, but seems most likely - did their draft research just by pulling their own list of rookies, rather than using the availables list.  Osteen wasn't drafted until late in the 1st round, probably several picks later than he should have.

That is part of the reason why I list my available in three parts:

Rookies
Undrafted from the previous year
Cuts

It's really only important the first season or two but it does help if you don't do all your research at one time.   Also, names stick out in smaller groups.  I honestly don't know how good Claude Osteen is but I know the name (I think because he was a pitching coach) and probably would look him up the first time though if I noticed it.