This NPC in Final Fantasy XII blocks you until the game is installed

That’s cool as hell

Kinda reminds me of the road blocks they use in Pokemon games. "We dance for no reason, we'll disappear for no reason"

I've only used that PS4 feature to start playing on a partial install once or twice, and I wondered what was already there and how it would prevent me from going into parts that are not yet available.

That's an interesting way to implement that.