The elephant in the room.

[Adonai One]

Then what's all that stuff Ra says about graduation and needing to be able to hold certain degrees of light to function in each density?

That's just a prerequisite. It isn't the exclusive purpose. An entity can bring themselves to highest amount of light in one third-density incarnation with enough determination. How these densities are used, traveled is up to the individual entity. The levels of light are just there to signify what experiences can be experienced practically, like levels in a video game. At the end of some games, you can skip around the levels as you choose.