I think using the example of the harassment of Blue Badge holders and - far more so - a survivor of childhood abuse - to illustrate why someone with diabetes might not announce why they needed biscuits is not appropriate.
On two occasions in the last few years, I've had to ask for something with sugar in due to not having my usual emergency supply with me. I was clearly ill both times.
I would have zero issue explaining that I needed sugar, fast, and no - biscuits wouldn't be ideal, but would be far better than nothing. There's no way I would ask without offering an explanation, and I would NEVER compare my situation with the ones above.
I am in no way putting them on an equal level - my point was just that your own personal medical circumstances are your own private details to share or not to share, as you see fit.
Many people with medical conditions do experience hatred/discrimination/abuse/patronising and thus prefer not to disclose it unless absolutely necessary.
Even with something like pregnancy, which is obviously not an illness at all, plenty of women in the early stages prefer not to tell other people for any number of reasons. It's their body, not a public right of knowledge. Some people are happy to tell others; some people prefer not to - both are valid individual choices.
If he was experiencing a hypo, it probably would have been obvious. My money's on him checking out your boundaries and I agree with your DH.
You're very probably right about that - I just don't think it's the one and only possibility and that we can rule out all of the rest.