Yes/No/Technically.
As I said before, having a harmonious empire is what makes you effective at Unity.
Arguably, beign harmonious is far easier in a small, tall empire. But, depending on the toptions and strategies we have avaible in Utopia, it might be possible for a wide empire to be harmonious as well.
My point is, if we say 'tall/wide affect Unity efficiency, because they affect it across 2 links by determining how much ethical divergence you suffer' we can go ahead ans say stuff like 'having many ships makes unity worse, because it allows you to conquer more, thus leading to more wide, thus leading to more ethic divergence, thus leading to less unity efficience'
Or append 'having a lot of minerals' in front of that whole chain.