Pretty much. But to be clear, when I'm talking about memory allocation, I'm talking about increasing the maximum mesh loading capacity of the clothing Slots via customization_slots.xtbl. Increasing that capacity has no effect on this bug. It just allows the Ronin Jackets to be rendered in that Slot. I don't know why the game can't handle applying both meshes at once. I guess it's an engine limitation. But it could be something else for all I know.
Also, just to add; When you're previewing another Slot (like Belts), Undershirts, Overshirts and Coats are hidden so you can see what you're doing. When you move to preview a different Slot, they'll reappear. In this instance, those Slots are hidden, not unloaded. The crash would not occur when the Overshirt and Ronin Coat reappear simultaneously. This proves the issue is to do with loading the assets, not rendering them.