Because remember, Parks committed to Tulane out of JUCO and signed a LOI with them. Then, when Cohen came on board, he wanted to go to State, and Cohen was fine with that, but Rick Jones, Tulane's coach didn't want to release him from his scholarship, and wanted Parks to sit out this year.
Cohen was able to work something out where he was eligible to play this year without sitting out, so that probably involved Parks walking on.