If they rated the 5th-8th receivers the same, or close to it, it makes sense to move back. It makes even more sense if they had a pretty good idea the one that may have had a slight edge in the Bills FO minds would be there to be taken as the 8th wr in the draft...
Back up RB in our system is going to get plenty of action year one. So, yeah it's a position that makes sense to solidify and even upgrade a bit if possible. Sounds good for where he was taken...