"Vault Dupe Protection Based on feedback we’ve received from the PoC loving playerbase, we’re implementing the following change! We’ve now Implemented duplicate protection on gold and platinum cosmic vaults to ensure that players don’t receive champion fragments for champions that are already maxed out."
From the the patch 4.6.0 notes From this note, I get that the protection is only for champions shards
This is correct. The relics are a bonus that aren’t normally in gold vaults, they just appear as an extra sometimes - an extra relic or a bit of extra stardust.