Professional fighters developed from basic stances. They modified this stance to accommodate their individual strengths and weaknesses, that's how they evolved to pro fighters. They are outliers by definition.
In other words: It does not make sense to copy others on this level. It would not allow you to develop your own strengths and weaknesses. Yes, if you reach a very high level, you would eventually give up this exact stance, but it is the well-balanced bread and butter and should only be modified if one knows what you gain and what you give up by doing so.
Thus, if what you ask is about learning how to box: Get a good coach and they will let you train exactly this stance, because it is the perfect compromise between offense and defense and trains a lot of things you tend to forget in the heat of a fight, which means you lose strength or speed in your feet and punches (knees bent, weight on balls of the feet and centered, shoulders relaxed) or open up for hits to the ribs (tucking the elbows in!) or head (hands up!).
A last word on McGregor: He is not a boxer. Mayflower played with him because it was a promotional fight. Would not have looked good if it lasted only for one or two rounds. And he is an extreme show-off, ie. he purposely shows an open stance and gives up defence to demonstrage just how "good" he is (as very good boxers sometimes do). But what you do not see is that they read the distances and only do so when they know they are out of range for the opponent. That is not what you should take as a blueprint for your boxing.