I know some people are wondering why you have to complete the sim to get to the little vault they have full of high tech goodies and I've come up with a decent explanation I think a few will find quite fair. The reason why there is tech in the vault is purely for reference only, when Sim-U-Tek was making the sim under contract from the military it was only natural they would want references to equipment used both by the American and Chinese military in the actual battle, so the US would provide them both known and secret equipment deployed by both sides in the war. Now the reason you have to complete the sim to open the vault I have only a speculation, my guess is when the air raid sirens went off on that day in October of 2077 in an effort to keep the valuable technology from being seized by looters and scavengers in the few years to come ( They probably didn't even anticipate people to survive let alone imagine the Raiders or Super Mutants of 2277, let alone the Brotherhood of Steel Outcasts ) a few employees linked the computer to the vault door to the simulator and removed the failsafe program so anyone without proper military training or without superior computer knowledge ( comparing your character's knowledge of computers even if it is 100 compared to a pre-war scientists skill with computers or technology is like comparing a caveman who has just discovered fire to a man four thousand years in the future who's unlocked the secret of converting humanity into an infinite free energy source ) would not ever be able to obtain the secret technology that had been lent over to Sim-U-Tek for references to create the sim.

And that is my theory on the tech vault and why you had to complete it in order to open the vault. Another noteworthy thing is they "likely" had some sort of alternative device that allowed them in pre-war times to access the simulator much like the pip-boy allows the lone wanderer too except the pre-war scientists probably took off fleeing with the devices when the bombs dropped, the reason the pipboy works with the sim could be purely, albeit a very fortunate coincidence.

but your education was from the vault, not the wasteland, and james was very smart and he didnt even grow upwith a vault education.
and perhaps this sim was a orototype of part of a vault where the simulated needed to be completed in order to get to the guns AND the vault exit, so those who were in the sim had proper training

In the end it does not make sense, the only explanation I can think of following Occam's razor was some programmer went nuts and rigged the door to open only when the simulation was completed and nobody come around to fix it.

Besides that anything that tries to explain the way the door opening is just contrived using assumptions that rely on jumps of logic because it simply they never explained why and it does not make sense.

My guess is it was a training simulation for US military, and once a soldier had completed there training they can go get weapons, im not sure why the saftey protocols are disengaged maybe after 200 years the saftey systems have decayed