If you started March/April this year, that may be somewhat true. Each day another set was free, and the free set rotated a few times through all existing ones.
But on any given day, it was the base set and that one set, not all sets at the same time.
Ah, yes you nailed it. It was during March I think right after pandemic lockdowns started. And I didn't notice which sets it was, but it def could have been base and one...
Ok, going to go see what it costs to have more sets.