I am with
@Hedgemonkey on this.
For a start, one does not stop at the exit of roundabouts, one is supposed to find a safe place to stop, cyclists and cars alike.
For a second, quoting on memory from Cyclecraft, text for our national cycling standard courses, if you are wobbly you're meant to practice somewhere quiet like a carpark until you're not wobbly anymore.
For a third

again according to Cyclecraft "anybody with an average fitness and road training can keep up with motorized traffic" (says also something about having a bike with gears) - this, imo, I read as that if you have not an average fitness or if you're unsure of the rules of the road, you cannot keep up with traffic, hence you should not, as a cyclist, be on a busy road.
In an ideal cycling world motorized traffic should be vigilant for vulnerable road users, of course, but this is not happening yet.
In an ideal cycling world Pat 5mph should be able to ride along Mr. Strava KOM on the local busy dual carriageway.
In practice he glides along keeping up with the flow, while I get beeped out of the way.
Mind, both of us could get run over at any time!
This train of thought by some forum members that think all cyclists should use any road just to prove the point that we are allowed would exclude kids, the less able bodied and the faint hearted from cycling.
Anyway, the cyclists in the OP might have been lost or there might not have been an alternative road to get to where they were going.