It's clearly not "the most obvious assocviation with flannel wasicoats in the Georgian era" and I have never tried to argue that it was. That's my point. It's not the most obvious association, but it is a possible one--not a secret one--and something Marianne has not considered. The History Wardrobe ladies did not make this up. There are contemporary references to flannel waistcoats being worn for hunting and by military men. Even though the ladies at the History Wardrobe did not quote chapter and verse to us during their presentation, surely they did not just invent this out of their fancy! Given that research into historical costuming is their livelihood, I'm sure they were able to find at least as many references as what I have found. Granted the references are not nearly so numerous as what you have, but they do exist.

I have never disputed and do not dispute now that wearing the flannel waistcoat was something that was commonly known to be the province of invalids.

But, if the main attribute is to keep warm and the garment is being worn by a person who does live on a country estate, who is in the military, who is not old and who does not have gout and other infirmities of the kind that take people to Bath or wherever, then a country (military) gentleman wearing it for outdoor pursuits to keep warm is not necessarily because a person is an invalid.