Puka had only been trained at one WR position at that point in his rookie season. McVay emphasized several times that Tutu was the only one who had training across all three positions.
If you don't understand that the WRs have specific roles in the offense, your football knowledge is lower than I thought.
I'm out.
Edit: Also, "Puka only played as a rookie because of injuries" is a complete misrepresentation. Figure out why.