One potential complication.
In 2002 the length of time to substitute a disqualified player was 30 seconds.
A buzzer is supposed to sound 15 seconds before the end of the half minute to provide some warning.
They changed the length of time from 30 seconds to 20 seconds at some time, but they still kept the warning buzzer 15 seconds before the end, so that means one someone is disqualified, five seconds goes by a buzzer sounds, and you have 15 more seconds to make the substitution.
The complication is that they dropped the substitution time to 15 seconds a couple years ago or so, but they left the warning buzzer margin at 15 seconds. So this means if you're going to give a warning buzzer 15 seconds before the 15 second limit, you have to sound the warning buzzer immediately as the disqualification occurs and I can imagine some coaches not recognizing that the immediate buzzer is a 15 second warning.
I didn't actually see Dawn during this. So I don't know that her failure to provide a substitute in time was due to a misunderstanding. Some have suggested she was being stubborn (I'm a big fan of Dawn but imagining that she is stubborn is not hard). However, I don't know whether those suggestions were based on actual knowledge or supposition or something else.
I do think there is potential for confusion and if they what the limit to be 15 seconds, I think the warning buzzer should be maybe with 10 seconds to go. Sounding a warning immediately is kind of useless, if you think about it.