I don't think it's multiple purchases to play the game. The beginning of the game is free, then there's a single purchase to unlock the rest.
It's the same as the old "free demo" model.
Another recent example of this working pretty well is Dragon Quest XI. The demo allows you to essentially play the full game, with no restrictions, for the first 5-8 hours of the storyline before you purchase to progress further.
Of course, the risk in this model is as follows:
Someone hears that DQXI is supposed to be good, so they go to try it. There's a demo, so they download that. They play for ~5 hours and realize they're not having much fun, so they stop playing before even being prompted to pay.
If I was a developer of the game I would say “well, that was working as intended, this clearly wasn’t the game for you”.
If I was a bean counter, however, I would say to axe the demo and add some micro transactions to the game. It’s a bad idea to let people try it beforehand and make their own decision on whether the game is good or not. Clearly we haven’t traded enough goodwill of our players, excuse me, customers, in exchange for some short term profits.