It has never been advertised that equipped items aren’t part of the eligible bonus loot rolls, and before selecting you may see the actual list as well before opting to go through.
Once you use a voidcore it removes it from the bonus rolls until the whole list is bonus rolled for.
If you want to give feedback about this you may opt to recreate this post at a different non-support forums as feedback is not collected here.
Edit:
You also posted in the main thread that addressed the fixing of the bugged loot rolls and how there could be duplicate rolls. If you believe something is bugged you may fill in a bug report through the ingame bug reporter or at the Support > Bug Report subforum.