I think it's explained well enough. In fact, the system we designed prior to either of these books print for our Adventurer's Guild bonuses in Dungeon of the Mad Mage is a nearly exact match to the Guild Patron.
For new players and DM's, simply using a template is going to be an easy and quick solution. For those edge cases you mention, you're likely already becoming or are an experienced player and adjusting the rules should be something you're familiar with now.
For 5e, rules don't need to be introduced with a huge amount of detail so long as they're functional and have room for tuning. That's kind of how the system is designed.