Actually on rereading the article I am going to play devil's advocate. It's not clear if his ex partner, or any other adult, was at the scene. It's also unclear (but implied) that his young children were in his sole care at the time of the severe hypo.
I have never had a severe hypo with my young children in my sole care. I would consider that to some significant extent I would have failed as a parent if I let that happen. I consider it a failure of sorts even to have allowed them to once partially witness it, because it can be pretty distressing (fitting etc). As a parent I do everything I can to prevent that situation arising. It has completely changed [my] whole attitude and approach to hypo prevention. It sounds like this guy also has a lot of measure in place - app on his phone, teaching the oldest child (only 5) how to phone in an emergency, maintaining safety arrangements with his ex. Nonetheless, accidents can happen. If, hypothetically, the guy was in sole charge of his children and lost consciousness, leaving the eldest child, only 5, to call his mum who called the ambulance, that is putting a lot of distress on the small children, leaving them without adult supervision and handling a medical crisis on their own - maybe in a public place, we don't know? - and I can see why the NHS staff responding could be quite upset.