I don't know why the advances don't show up in tech tree. Currently in age 2. I can research it using console, so it is coreectly loaded (?). E.g. I can run `reseach deus_vult_adm`.
I already tried with disabling all other mods except this.

@Hoppy
I won't say I noticed that issue. But you can even see on the first picture above that an item "enforced_service_dip" that should requires "open_levy_standards" can be researched. So it's more like, it was available at the wrong place and not in the proper chain making it blob.
Fixed the issue and now it is the proper chain in the proper place instead of randomly.

There are some advances that don't show up because the tech requirement name isn't updated in the modded files. For example, Benefits for Mercenaries in Age 2 doesn't show up because it requires debt_and_loans instead of the updated name, debt_and_loans_adm.

So does it give AI all advances from the 3 paths as well, or is it only for the player?

@MrBlazzar™
Yes, I modified the description. In short, Paradox themselves in the file have a comment saying
#Note : This does not seem to apply retroactively
It's only from the moment you have it. And for a lot of stuff too. You could fulfill the condition 1 day before and 1 day after something but if, when the even fires, you do not fulfill the condition then it will not apply/activate/fail.

Unfortunate that it doesn't seem to work on already in progress games but look forward to giving this a run on my next game.