Not so important if you are staying onsite but important if you aren't. For example, Minion Mayhem. If EE is at Universal, MM has a long line before the park opens for offsite visitors. If you are a family that really wants to ride that ride, planning your day around it can make a big difference.
We will be there 11/8-9. We called universal last week about something else but asked if they knew which park would have EE and was told that it would be IOA both days.
I've never seen it be only Universal. If it's only one, its been IOA from what I've seen and read here.
Since two different people got two different responses, it looks like you may have to wait until you are there to see for sure.
I have seen it when it is only Universal , but I agree.You may have to wait until you arrive. Our last trip we were told it was Studios only for our whole week.On day 2 they changed it to IOA only and without prior notice