So during a queue, i checked my armory and noticed that all of my armor, at least chest armor, was unlocked. Just to check I equipped the HP/Parafoil [R] chestpiece, and then we loaded into the game. I expected this selection to revert, but on completion of the match it didn’t.
Here’s a link to a screenshot of my Spartan in the armory with the chestpiece equipped, note my rank in the top right. The tier of the season you unlock this armor piece is 89, making it impossible for me to currently own it.