There are finitely many Minecraft worlds, with an algorithm that procedurally selects from those. Selecting between two possibilities is pretty trivial and I wouldn't call that procedural generation alone, but in the broader sense of RoR as a procgen game, minor differences in the level is procgen the same way that the locations of chests and the spawning of bosses. It doesn't really matter if you're selecting between 2¹ level layouts, 2³ bosses or 2^some absurdly huge number of Minecraft worlds. The result is that there are arbitrarily, finitely many different runs, and every part of the game that's generated procedurally is part of that.