Crystal (Term) - The Final Fantasy Wiki has more Final Fantasy information than Cid could research

On this wiki page it states that
In Final Fantasy IX Crystals are the source of all life; the Crystals residing at the center of planets circulate life, from which all life is born, and to which the souls return upon death, and as the memories of living beings accumulate inside the Crystals, the planets grow. Eidolons in Gaia are guardian spirits created by the Crystal in order to protect it. The people of Terra had mastered the art of fusing their Crystal with others, allowing them to assimilate other worlds and keep their race thriving even when their current Crystal weakened. As revealed in the Final Fantasy 20th Anniversary Ultimania<sup id="cite_ref-0" class="reference">[1]</sup>, once a Crystal has aged, it returns to the cosmos and becomes the source of a new Crystal. Crystals also appear in the game as a means of summoning Eidolons. The four "jewels" sought by Queen Brahne of Alexandria were in fact fragments of a Crystal broken apart 500 years prior to the game. If all four jewels would come together in Alexandria, Alexander would be summoned. This echoes Final Fantasy IV, as Alexander heavily resembles the Giant of Babil, which was also summoned by a gathering of Crystals.
Also, Crystals can be equipped as Add-ons, which grant the user special abilities, particularly for Dagger and Eiko, who can learn Summon Magic from them. Eiko can also alter her Summon Magic according to the gemstone she has equipped.
I was wondering where some of this info came from. It states the Ultimania as a source for one section referring to the aging of a crystal, but what about the rest? Is it to be assumed that they all came from this one source? If so I didn't see much allusion to it in the game and by this info it sounds like Memoria was a portal to Gaia's core.