One dynamic I experienced that also isn't in the simulation: if you focus too much on classwork early on in order to pass your RPE, it can actually be hard to find an advisor. Classwork is basically dead-end work and the more you focus on it the less you have to show for yourself when trying to convince an advisor to work with you. Your goal should be to optimize for doing just well enough to pass your classwork.
Also, random catalysmic events, like in year 4 your advisor accepts a job at a different university in another state.
Also, random catalysmic events, like in year 4 your advisor accepts a job at a different university in another state.