It's saying you can control them progressing through the story. Where is the monetization there?
It doesn't say you control them progressing through the story. It says you
encounter them as you go through the story. "
Not only CAN they become your allies, you will be able to control them yourself." These are two separate sentences, implying a distinction. At least that's how I interpret it.
Furthermore, you can also play as various banner characters in the story segments in games like Zenless Zone Zero. Then those characters are locked up again. You play a quest or two as that character to get a feel for them, and once you're hooked, you waddle over to the store and you can roll for them. This is nothing new in the mobile sector. You give players a taste, and then you get them craving more.
This is why all predatory monetized games start you off with tons of energy or materials and fast level ups and oh wow here's a four star <thing>. Jeez you've only been playing for a half an hour but you're already level 5! Ah well... looks like you're out of energy now. See ya tomorrow! Well unless you want to keep playing... Tell ya what, just for you, I'll give you an introductory deal. For 99 cents I'll top up your energy three more times. Then you can keep playing and keep having fun!
There's a term that escapes me right now referring to the psychological barrier of the first dollar spent, and once a player crosses that threshold, it's
much easier to get them to continue spending.
I'd be willing to bet that when this game launches, you can create a character and play as normal, but you're locked to whatever weapon type you started with. You can unlock more weapon types as you progress through the quests, but kitting out your character will be a long, arduous process. Looking back at MH Frontier, you would need to hundreds of materials to create a single piece of end game gear. Of course you could always pay real money and skip huge chunks of that. I mean, what's more important, spending $5 or 40 hours crafting this thing? And then the banner characters, on top of being cool, already have their own unique armors and weapons with skills and set bonuses that you DON'T have to grind for yourself!