Well in Seble's development blog, I found this
post in June 2012 about the changes to the EE logic:
Just a quick update: I've been doing some further testing on the rule that prevents early entries once a team has lost 5 players already. After my testing, and the forum feedback, I've decided to bump up the number to 6. That change should lead to more underclassmen leaving.
I'm still considering tweaks to account for senior transfers, but haven't made a decision yet on that.
A few hours later in his next post, he states:
I've decided to exclude all senior transfers from the count of leaving players with regards to the previous post.
Notice that he doesn't mention class except for the senior transfers. I do believe though that it has to be a player that has a scholarship so walk-ons are excluded as well (but players leaving due to lack of minutes would be included).