You sir are correct
The Practice Squad shall consist of the following players, provided that they have not served more than two previous seasons on a Practice Squad: (i) players who do not have an Accrued Season of NFL experience; and (ii) free agent players who were on the Active List for fewer than nine regular season games during their only Accrued Season(s). An otherwise eligible player may be a Practice Squad player for a third season only if the Club by which he is employed that season has at least 53 players on its Active/Inactive List during the entire period of his employment.
Obviously, Easley does not meet the criteria in (i), as his two years on Injured Reserve mean he has two Accrued Seasons, given that players on IR are paid their full salaries. It's in (ii) that it appears Easley qualifies for the practice squad, as he very clearly has fewer than nine regular season games on the team's active list.
http://www.buffalorumblings.com/2012/8/25/3267906/buffalo-bills-marcus-easley-practice-squad-eligibility