This video shows a coach spotting the tap swings then re-positioning himself to spot the flyaway
The coach in that video is doing the absolute most he can to be ready for a possible accident. That's what every coach should do, at all times. It is the coach's job (literally) to be there in case something goes awry. However, peels can happen on other skills too, and at any time. Even if a gymnast has
never peeled, it could still happen. Judgement must be used, taking everything into account on that given day.
"Statistics are no substitute for judgement."
In my opinion, if a coach isn't standing in during a bars routine, they are being negligent. In optional levels, standing between the bars for the duration of the whole routine is a 0.1 deduction, so in this situation the coach should move in and out as necessary, based on each individual gymnast.
And I have a bit more to say about the deduction for standing in at optional levels… what a stupid rule! I understand that it exists so the coach does not get in the way of the judge evaluating the routine, which is a valid point. Coaches should stand in at the far side so as not to obstruct the judges' view, and the deduction should only be applied if they are blocking the judges' view.