I can adjust to higher temperatures just fine, but not sitting still (even with regular active breaks) at anything below 21°C. Our company used to rent office space when we were a startup in a place that didn't turn on the heating until temperatures outside dropped below a certain threshold. Sometimes this meant 19°C or 20°C for weeks: I don't get used to it; it just stops me being productive (and nice).
In most situations, I feel like people talking extensively about grit assume the difficulty level is the same for everyone. And they tend to be antagonistic towards people who try to explain why some things are more difficult and instead double down on pushing grit.
I wonder how many people feel that way. I've never heard of anyone having to take a hot shower to keep warm in a 20°C room no matter the clothing. I wonder if it's just a taboo, something that simply doesn't come up, or if this happens to one in a thousand.
As for tall and slim, I'm also Dutch so I imagine I'd have heard of this more than zero times before if that were the main cause.
19°C is fine if I'm remodelling, hoovering, doing the dishes, or anything else that involves not sitting behind a desk, and I don't mind being out in freezing cold as long as I'm moving and have very, very good gloves on, but working behind a desk with my brain requires my body to be comfortable, relaxed, and not annoyed by stiff fingers hitting the wrong keys.