Attribute change being "possible" doesn't mean it has to be "free".
It can be possible to change attributes, but it can be BOTH limited by long cool down, and super expensive, so it will also require considerable effort on your part to be able to do it.
So group block can still play knowing that choice has tangible consequence, and group free can eventually change their attributes if they will not like their current ones, they will just need to place some effort in that, and not get it for free.