As you say, I guess the biggest issue with diabetes (insulin dependant) is the risk of incapacitation due to mis-calculating the amount of insulin taken with the amount of carbohydrate consumed. I bring my own food to work as the crew food supplied to us isn't labelled and I don't really fancy guessing carbs for the very reason of misjudging the insulin required unless it's food with standard values such as bread in a sandwich. I usually have food very low in carbs, or have zero carbs. Peanuts for example. I was telling my consultant this and he did say there is potential for the body to convert the protein to glucose if not consumed with carbohydrates?
Anyway, keeping an eye on things once I've eaten isn't a problem with the CAA testing protocol (within 30 minutes of take-off and landing and every hour during flight). I'll then use that instantaneous snap shot of my blood and couple it to the trend arrow on my Libre to get a pretty solid understanding of where my sugars are heading.
It's just finding that balance of keeping sugar levels from going low and from keeping them running high as to cause long term (and short term) issues.