Sorry you are incorrect. The game does indeed stream some assets in but it mostly terrain, static NPCs, etc because those are predicable and don't need to be tracked by the sever allowing for local pre-loading prediction from the HDD.
Character assets are all pre-loaded into memory. This is why gearset changes are (near) instant(there is still a memory load function dictated by memory bandwidth) in FF14 and doesn't require a model reload unlike how it was in FF11, even on the PS3. They've already also specifically stated memory concerns with character models when they brought up the issue of separating Ar'Ra horns. Not to mention the original release of ARR was pushed back with the team specifically citing memory constraint issues with the PS3 version. There is also the mention of hud changes being restricted by the strict memory constraints of the PS3.
You can't reasonably stream in so many assets from a hard disk into memory that are unpredictable as having to render local players with any various amount of gear options that are out there. The servers have no way to track that much detail on players that are beyond the already small object render distance. The load fade in time for players coming into rendering view is the delay it takes for the engine to fetch the assets already in memory and with the PS3 split memory architecture, the main system memory is likely just functioning as a memory cache for video RAM. If the game was actually fetching player assets from the hard disk then the game would constantly hitch every time it needed to load a new model coming into view and that simply is not happening even with a slow 5400RPM hard drive in the PS3. That should make it plain as day that most if not all character assets are pre-loaded into memory meaning they have to work within a memory constraint budget to make sure they can fit it in along with whatever non-character assets need to fit in along with it such as terrain, monster, NPC and UI assets.
This is absolutely a PS3 memory constrain issue which is just one of MANY game design decisions that have been made around the constraint.