
There are four power systems in play in this universe. Swordmasters use mana. Sorcerers use magic. Those blessed (some are in the Church, but not all) use holy power. These 3 are all different and have been around for a long time (there's more to their history, but that would be a spoiler). Suddenly the Red Stone fell and Awakening came to be, as a fourth power. It's pretty new, at this point in time it's only existed for a couple of years and people don't fully know how it works yet.
When he uses fire and water it's technically noy "fire and water magic" but "controlling water and fire through awakened power". Like, you could technically use mana as a swordmaster to launch a wind attack, but you still wouldn't de using wind magic. They called him a liar because sorcerers limit themselves to only one element because magic of different elements can crash one against each other and is thus really difficult (they usually choose ONE and adhere to that one), but since what he's using isn't actually elemental magic that restriction doesn't apply to him. His ability is actually waaayy stronger, all natural matter is fair game for it.
I hope I've explained it clearly :)

novel reader here, yes! ppl were able to use magic before the red stone, although it was more difficult and rare. the reason the examiners called him a liar is bc magic used to be so hard to master that practitioners usually stick to only one element/attribute when studying and using magic. for example, before the red stone, water sorcerers could only use water magic, while fire sorcerers could only use fire magic etc etc.
I have a question about the world building. Were people able to use magic before the red stone or after? It has me a little confused because there is a divine sword and sorcerers that were around before the red stone dropped. Also at the beginning of the webtoon when the MC applied to get into the legion, his examiners called him a liar when he said he could use fire and water magic.