I'm about to come up on my 5 resets quest step for the broadsword and Bungie stated this is retroactive however I reset my Valor rank 5 times last season and have the associated Triumph for that. Does that count or do I have to reset my Valor rank 5 times this season too?
You'll have to do 5 Resets in this season again unfortunately.
The Quest was retroactive if you reached the Quest Step for the 5 Resets in the Season you achieved the 5 Resets in.
In your case, you achieved 5 Resets last Season, but you didn't get to that Quest Step, so your progress towards that step was removed.