Oier didn't even need to expand on his last statement. The footage was proof enough.
In it, magic was split into two states. Mana and Mageia. Most players gathered mana within themselves, slowly moving it to the outside world, keeping it in shape with their Mageia, and then activating their spells.
Conversely, Eldrian sent out his Mageia without mana. He used them like feelers, seeking out his surroundings. And, when the time came, he used those distant tendrils of Mageia to gather mana from his surroundings and form his spells.
This last step took longer. Naturally so. The density of mana in the environment was limited. But with his control, he could expand his zone of control to call in more mana. Lessening the time requirement at the cost of some more focus. But it still took longer to cast this way than normal casting.
And while it was a completely different method of casting, it was not an unknown one.