Correct. The right course of action would be to backtrack this per download idea completely, fire the person who thought of this, and add a clause on their ToS that such bullshit will never happen again, and that of they broke that agreement, they will refund everyone affected by it.
OP is using a strawman, but it’s a reasonable one. In an ideal world, if a company offers unlimited data, then changes its mind, the least they could do is, I don’t know, ship the users’ data in SD cards for free.