I'm pretty sure someone already mentioned this, but:
Keys still get deducted when you try to play a new chapter, unfortunately.
Character creation at the beginning of each book still costs gems for players who might want exclusive hairstyles or to start with exclusive outfits, but every choice after that is free.
I know it might be shocking and give the idea the mod doesn't work when the first diamond choice you make has your keys getting spent, but it 100% works!
It's a great mod. Not having unlimited keys make it hard to keep interest in the app for me personally but it's still way better than forking over money to PB especially since they got rid of the 100 ads option for diamonds.