How does Luminarie spell tome/spell creation differs from other ways of creating spells grimoires?

In ESO we have been introduced a new way of creating new spells with Luminaries (beings of pure Magika) and using their special inks.

I understand as magic has infinite ways of application and spell/rituals to creating new ones but what I am confused about how does THIS is a special method?

Spell making is nothing new to many many mages and organizations as we see in all TES games and lore.

Obviously in-lore spell books aren't consumed to learn the spell. Grimoires are just tomes written usually to contain many spells, rituals, theory of the magical arts etc. They are tools of learning. So how does luminous ink makes one 'better'?

Is the spells created by using powers and gifts of Luminaries dependant on them? Like if they once more retreat from the world will the spells be ubusable?