Class is being used to describe what the character does. In this case, from the majority of fantasy settings and historical things I know about, "paladin" was used to describe a holy knight, and sounds better than just saying "holy knight".

In terms of my setting a paladin is a religiously-motivated knight who uses holy symbols and often enchantments on their weaponry tied to their deity, in Tanya's case the divine fires of Reon granted to Repharion.

As this is not D&D I assumed people would take paladin to simply mean "religiously-motivated knight" as it does in many non-D&D settings and not begin arguing over the definition of it.