You are probably mixing up pomelo and grapefruit.
They were sold as white pomelos.
Two supermarkets here have surprising amount of variety, even though it's far outside of commercial citrus growing territory.
(Page mandarin, mandarinquat, Buddha's hand citron, even Yuzu, just to name a few)
They were also bigger and more pomelo-like than the white grapefruit I have seen them sell.
I know the difference between grapefruit and pomelo. These could have been a pomelo.