If you unlocked special armor in beta (example: herioskrill) it will not show in halo 5. The good thing is that you can still use it.
What? Potatoes? I don’t understand.
All armor unlocked in the beta did not carry over to Halo 5
BUT the armor you get through achievements in the MCC was usable for the beta AND the current game so that would include Helioskrill.