This is not true with most roundabouts in North America at least. If you look at the diagram GP posted, you do not change to the outer lane to exit. You exit directly from the inner lane. In fact, you NEVER change lanes in a roundabout. The reason this works (where the inside lane crosses the outside) is because the roundabout is small enough that the traffic in the outside lane has to let you exit as part of yielding to enter the roundabout in the first place. After that, as long as everyone respects which exits they're allowed to take from which lane, there is no more crossing traffic. In practice, if you are in an inside lane, you want to keep an eye on the outer lanes to make sure someone isn't trying to take a later exit than they are allowed.
From GP link:
> Do not change lanes in a roundabout
> Do not travel in the outside lane further than allowed as it may create a hazard for the vehicle exiting the roundabout from the inside lane
When you exit from the inner lane you necessarily have to change lanes because the inner lane is completely inside the outer lane. You may not think of it as a lane change because you're going across the lane not merging into it, but it is a lane change and you have to pay attention.
No, they have to yield to YOU because you're already in the roundabout. It's hard to believe, but trust me, this is just how it works and all of the links I've posted agree. The reason why it works is because when you're in the situation you describe, for the person entering at the second exit to be a factor, they would have to be entering as you're already alongside the second exit and in the process of exiting at the third. So they need to be yielding to you as they will be crossing your lane. Part of waiting for the gap is waiting for the exiting traffic to clear. Not for only YOUR lane to be empty.
Here's a video from Minnesota timestamped to them talking about exactly this scenario in detail. Namely, yielding to all lanes of cross traffic: https://youtu.be/CEhNboz5GPk?si=LxdVQZx0MHrYhl8w&t=196
> With multi-lane roundabouts, it is important to stop for vehicles in all lanes of traffic. Wait until there is a gap in all lanes of traffic and then enter slowly. Never try to enter alongside cross traffic or assume any driver's intended path. One of of the most common mistakes people make when entering a roundabout is failing to yield to all lanes of traffic. Yield doesn't mean just slow down or merge. Yield means that you must wait until all traffic in the roundabout has cleared before proceeding. Make sure that no one is in either lane of the roundabout and then proceed.
The video also has a good overhead view that is better than most at showing the scale of the roundabout. The important thing to note here is that to enter the roundabout, you have to cross the lanes that are exiting, not merge into them. So you are yielding to all exiting lanes.
The person following the outside route from 90 must yield before even entering. It's very confusing until you're actually in them, but they're small enough that what you're saying usually isn't really a problem (at least in well designed roundabouts). When the car at 90 enters the roundabout intending to take the 270 exit, they yield to traffic in ALL lanes that might be exiting. Not just traffic in the outer lane. If they were intending to take the 180 exit, they only need to worry about traffic in the outer lane (or people incorrectly changing lanes when exiting).
The 90->270 car sees the right indicator and lets the other car passed.
The real answer is somewhere between the above and the 90->270 car waiting to enter the roundabout because it is not sure if the other car is actually going 0->180 or 0->270 because they are a shit diver that doesn't indicate on roundabouts.