This Chapter confirmed something.

[Xēnovia.]

Even after gaining EMS, Izangai's effect still seals off that eye off. I think the help of Hashirama's cells help restore that eye when he gain the Rinnegan? It sure looks like it. ​

 

[TheAncientJinchuuriki]

Looks like Hashi's cells are the helping cause in the Kaguya revival

 

[llxFLaMe]

Yea I think so or it could be the sage chakra

 

[Memento Mori]

Yes that is why obito didn't got blind by overusing Kamui