What defines an overdose is the impact it has on your body not the specific quantity consumed. Thus you can OD on insulin even if the amount is needed at other times.
If they had taken that much at home it may not have resulted in an overdose, but in this situation it did.
Well, by that logic, if someone has a panic attack from consuming cannabis, you'd view them as "overdosing" on weed.
I suppose you're free to say that, and everyone else is free to ignore this as ridiculous nonsense which is completely out-of-step with the widely-used definition of "overdose".
You're completely ignoring the context of the event. Have you ever been to a rave? Some promoters are good and understand the importance of providing free/inexpensive water, proper ventilation, and security who are able to spot attendees requiring medical intervention. Other promoters are shady AF and do none of those things. In the latter case, if someone consumes MDMA and also dances for hours without hydration and the venue is way too hot / oversold, yes that person is at risk of hyperthermia.
That can also happen even to sober people, I've literally seen it.
Try asking your GP about what it an insulin OD entails and they will refer to the results not the specific dose. Though obviously there’s a dose large enough it’s never appropriate.
If they had taken that much at home it may not have resulted in an overdose, but in this situation it did.