It seems to be common knowledge that enemy color pairs in Magic have less synergy than allied pairs. As an example, the highest score question on the site, What are the names for Magic's different colour combinations?, asserts without explanation that allied color pairs have "higher deck cohesion". Then it repeats this claim in explaining why wedges are generally less often seen than shards. But I don’t really understand why. It seems to me that every color pair offers something different, and many enemy color pairs seem very cohesive to me. The current meta in multiple formats seems to support this.
In standard the most popular deck right now according to MTG Goldfish is Izzet Prowess. And the 2 most popular modern decks are Boros Energy and Izzet Prowess.
I haven’t played much Canadian Highlander, but watching LRR’s North 100 podcast, it seems Jeskai is the most powerful color combination in that format.
It doesn’t seem like an outlier when multiple formats of varying power levels are dominated by enemy color pairs and wedges. Izzet Prowess seems like a very synergistic deck built off the payoff for slinging a lot of cheap spells. Boros Energy in Modern seems built off the back of several very powerful cards some of which happen to have Energy. But to me, Red and White offer a lot to each other. Red provides reach in the form of direct damage and card selection with rummage/impulse draw effects, while White is a better at going wide and gives non-damage based removal to deal with high toughness or non-creature threats.
Perhaps I am somewhat conflating power and cohesion, as my examples rely on high performing decks. And I do want to acknowledge that there is a bit of a bias with my examples, perhaps Boros and especially Izzet are just particularly well suited to each other among enemy pairs. However, other color pairs seem similarly synergistic to me. Simic pairs the card draw of Blue with the ramp of Green for a powerful big mana deck. Orzhov pairs the go wide power of White with the sacrifice theme of Black to be the backbone of many aristocrats builds. Golgari pairs the powerful mill and graveyard effects of Green and Black giving a powerful, recursive engine. All the enemy color pairs have a very solid synergy built in, in my opinion.
So can someone please explain where this seemingly common conception that allied pairs are more "cohesive" comes from?