User blog comment:Victory awaits/The actual outcome of Apocalypse?/@comment-87.116.253.21-20161002110418/@comment-1975828-20161003153348

You can interpretate Dean's words in more ways than one. He could be referring to Death as a sort of protection or shield. Death was their best weapon at the time, so maybe he was bragging too.

Dean may have also interpretated Death as being stronger than God, since Death said he would one day reap God.

There is also no evidence to say that binding Death means you have immunity to death itself. One could probably command Death to spare someone or ressurrect them. Maybe that's what Dean meant.