I'm gonna disagree with that. While a system such as you describe might be less authoritarian than one where the hierarchy is fixed in place, it still is a hierarchical structure - just one where your place is based on "how good you are at climbing the ladder" instead of "who your father was".
Well you're wrong. I only mean in the context of this game of course. Obviously I make no judgement about what political beliefs you may hold. But in the context of this game, you're so unbelievably wrong that I'm honestly surprised this is actually being debated on the forums for this game. The most egalitarian you can make your government is to have it be one of a flavor of democracy where a hierarchical structure is still observed, that is the concession made to the most ardent of egalitarians. Or to put it plainly, fanatic egalitarians still have leaders. And this isn't just a compromise to make them playable, effort was put into the formation of these governments so that how their leaders were selected was a component of their being. Maybe if you wait long enough anarcho-capitalism, or some sort of super individualism will become a thing in Stellaris, it will serve as a counter-point to Hive Minds and we'll get a government type that trades the leader mechanic for some sort of flat, or even randomized bonus.
Now, you seem to be operating under the impression that by showing something to have a form of authority, you can prove it's authoritarian and thus the opposite of egalitarian. But if you are to place to the idea on a continuum of egalitarian to authoritarian, we have to place the dividing point between Egalitarian and Authoritarian on the continuum that the game universe actually uses. And for that I refer you to your own post. Within the range of experiences that this game offers, a meritocratic hierarchy is as egalitarian as it gets.
While a system such as you describe might be less authoritarian than one where the hierarchy is fixed in place, it still is a hierarchical structure - just one where your place is based on "how good you are at climbing the ladder" instead of "who your father was".
But from what I can tell your premise is bad. Egalitarian and Authoritarianism, as presented in the game, aren't opposites, they're simply incompatible. It's an understandable bad premise, an axis line will do that to anybody, and it may even be defensible within the structure of the game, but it's not true to the definitions provided by the developers.
So, with that I requote the game's definition of Egalitarian again.
Egalitarian replaces Individualist and represents belief in individual rights and a level playing field. Egalitarian pops dislike slavery and elitism and prefer to live in democracies.
Nothing about individual rights or a level playing field is actually contradictory of the idea of a hierarchical structure. Particularly when we make it a merit based hierarchy where progression is earned, and not granted. A level playing field doesn't promise equal results, and individual rights don't promise that you'll never have a boss. The first just promises that you'll have an equal opportunity to achieve those results, the second that you'll be able to tell that boss where to shove it and walk out. The closest the game's Egalitarians come to your definition of egalitarian is a dislike of slavery and elitism, but within the game's own framework that really just means that the Egalitarians would like slavery banned and for everyone to be allowed to vote on who leads them in their respective hierarchical structures.
And continuing on this topic of Paradox's definitions, it's not hierarchy that determines Authoriarianism.
Authoritarian replaces Collectivist and represents belief in hierarchial rule and orderly, stratified societies. Authoritarian pops tolerate slavery and prefer to live in autocracies.
It's hierarchical rule, that is the creation of a hierarchy within government, specifically we see in their preference for autocracies, a hierarchy that separates political power and responsibility from the masses. And that's just the first part, they also prefer an orderly, stratified society. That's a society not mixed up by things like social advancement or blurred lines between social classes.