I think you are reading a little much into. You dont make statements to 7th round rookies prior to training camp.
We need depth a his position subtype. 6'4' 285+ pound guys will be the main horses on the Dolphins D-line. At pretty much any given time you can expect 2 of those type of players on the field. In the 4-3 they will line up at Undertackle and LDE, in the 3-4 they will line up at DE. In nickel and dime packages they can line up in the interior.
Having one backup apiece between the two main starters is just good sense. Two young developmental picks behind our two 29-31 year old starters.