iTunes save and restore does not restore purchases packs

I needed my children iPad for a workshop. I saved it fully using iTunes. Reset to factory defaults, then used it. Back, I restored it, still using iTunes.

Regarding Minecraft everything is there (about 1 Go of data), but lots of worlds are locked as all the children purchases.

I understood there was a risk if you remove your application and its data, but here I saved them before, in order to keep them. So I don't understand.

I have contacted customer service more than 48 h ago, but no answer. So I come here.

I've seen some other tickets, but it was about a Minecraft update. That's not exactly the case here.

Any idea? Should I upgrade iOS? Minecraft? Is this the normal behaviour?

Regards,