Hello!
The “What are AnkiHub’s recommended settings” FAQ is meant for users to understand what it means when they tick the box that says “use recommended settings” upon installation of AnkiHub decks.
These settings come from the butler add-on
When a user installs a deck from AnkiHub, they are met up with a pop up that says “would you like to use recommended settings”. If a user has that box ticked, it automatically sets the settings that are recommended. Here they are below
The primary reason for these “recommended settings” are for users that just want to jump in and start using decks without having to fiddle around with settings at the start.
Users can opt out of this upon installation of a deck. The primary reason for setting the learn ahead limit to 0 (from my limited understanding) is so when users click again, it does not show up right away and it has time to be “forgotten” and recalled in (15m) as per the settings we set. Nick or Abdulla might be better to ask on this specifically on why it’s set to 0
These settings are also what is recommended as part of this video for SM-2 (I can’t include links in posts but here is the YouTube video title: The BEST Anki Settings and Algorithm Explained (by an expert!)). Here we also recommend setting it to 0 unless it’s the end of the day and you want to see cards you have left over and you want to do those right away
The FAQ can be worded better. We are saying that the only thing we change is the learn ahead limit while the other global preferences are just set to default, the post does a poor job of conveying that. I will fix that, thank you for pointing that out 
I hope that clarifies a bit more!