What exactly happens during the sourdough ripening?

I am following a recipe from the well established Italian Baker Bonci, to make my liquid sourdough starter (with some success too).

In his recipe he says to refresh the starter with a 1:1:1 proportion every day for a month before it can be considered matured and ready to use.

I would like to know what happens during these 31 days and why this time frame is needed (the starter seems very active after a week or two and is capable of leavening bread already).

My understanding /theory is that the successive rounds of feeding, souring and re feeding help grow yeasts while acidity weeds out some of them, in fact selecting the right “genes” we want to keep in our starter.

I would like to know :

1. If my theory is correct and if it is
2. Exactly what traits/type of yeasts are we selecting for?
3. What are the typical proportion of a yeast types found in starter?
4. Is there any source describing the detail of this process (I’m interested in the selection part more than in the recipe part, but I don’t won’t a bio textbook)