This may be a reference to texture streaming. While I've never developed for consoles, I do know that texture streaming on desktop & mobile can be challenging.

Being able to mmap a texture directly from ssd (as if it were RAM), with the hardware & os taking care of all the details, could be a big deal for developers.

Edit: To get a sense of how challenging this can be, see this recent talk from GDC for texture streaming in Titanfall 2: https://www.youtube.com/watch?v=4BuvKotqpWo . Literally all of this complexity would go away if you could mmap textures directly from disk and let the gpu handle it.