For anyone who has been watch or reading this manga/anime for the past 15/16 years should know how the mechanics of how the sharingan works or the uchiha dojutsu in general.
First! We know when you activate the sharingan both eyes activate to its full capacity, meaning if the user has all 3T within his sharingan they are visible.
Now we have Sasuke who has the sharingan in one eye and a rinnegan in the other. So when he activates his 3T sharingan the original rinnegan is activated because it is taking the place of the original 3T sharingan.
He hasn't used his EMS witch would be why we don't see his 6T rinnegan. I think because it's a different activation just like sharingan to EMS.
So my theory is when he activates his EMS then we will see the 6T rinnegan because it is a different lvl of activation just like sharingan to EMS.
First! We know when you activate the sharingan both eyes activate to its full capacity, meaning if the user has all 3T within his sharingan they are visible.
Now we have Sasuke who has the sharingan in one eye and a rinnegan in the other. So when he activates his 3T sharingan the original rinnegan is activated because it is taking the place of the original 3T sharingan.
He hasn't used his EMS witch would be why we don't see his 6T rinnegan. I think because it's a different activation just like sharingan to EMS.
So my theory is when he activates his EMS then we will see the 6T rinnegan because it is a different lvl of activation just like sharingan to EMS.