Tribute summoning a card that requires 1 tribute as cost (lvls 5 and 6) cannot be summoned using cards that are treated as 2 tributes.
Bug reproduction steps
Try to summon any lvl 5 or 6 using cards that are treated as 2 tributes for a tribute summon.
I tried to find some related rulings but had no success, also the cards do say “CAN be treated”.
Screenshot OR error code
also tested with the earth Gaia.
Be able to tribute summon lvl 5/6 using cards that cheat tribute costs.