Hey, I'm already giving CFC more credit for physical health than I would to the population at large.
I just have a really low opinion of the physical shape of people in the western world, well over 80% of the population doesn't meet the minimum physical activity requirements for long-term health.
This. He is trying to say that the typical Fighter from a D&D Fantasy setting is far more active than the typical CFC user. This will be reflected in the Strength, Dexterity, and Constitution score. Therefore it is more valid to compare these average scores with average scores from people who are physically active.
The scores he gave might reflect a magic user who spends much more time studying books than in physical training. Strength would be reduced in order to increase the Intelligence roll. So the average score for Strength might be more like 9 instead of 10.5.
1RM PR deadlift isn't "mine", it's an official 5e rule. (Well, 1RM deadlift being by interpretation of "maximum lift".)
I do not have the rulebook, so I do not specifically know what it says. A deadlift is set up to optimize the weight that could be lifted. Say somebody can deadlift 300 pounds and there is a rock on the ground that weighs 300 pounds. Can he lift it? Does the rulebook say anything about how high this lift is? Is it a lift to the hips or to the shoulders?
At a county strongman competition, there was an event (Atlas Stones) where the person lifted progressively heavier stones to a platform about chest high. The stones ranged from 200 to 220 to 250 to 300 to 330. Most of the guys looked at the 330 pounder and shook his head. One guy lifted the 300 pounder and just used the 330 pounder as a stepping stone to jump up onto the platform to celebrate: He won the contest.
Would a Strength 10 D&D character be able to accomplish the same feat? How would a Strength 9 Magic-User do?
I can't recall if any of the other stats have anything similar - I'm at work now but I can check the PHB when I get home.
You would probably have to look up stat checks and skills and stuff like that. The questionnaires I saw tended to be way to subjective and yield numbers that are way too high. (Hopefully arguing about all of this is helping your skills as a DM - You probably have to have arguments like this all the time.)
Dexterity: List 5 simple feats, 5 challenging feats, and 5 amazing feats. Start at 3 and claim 1 point for each feat. Simple might be a somersault or a cartwheel. Amazing might be to stand at the top of a stairwell and do a back flip onto the next stair. Maybe the back flip is good enough.

Incorporate agility, balance, coordination, handwork, footwork, stability and stuff like that.
There is a lot more to dexterity than shooting them up in a video game. If somebody swings at you, are you able to get out of the way in time? Are you able to make him look like a fool while you are at it? Do you win finesse games like fencing? If you are throwing a ball, are you able to replicate that same throw every time?
Constitution: I put too much weight into mass before, but the questionnaires put way too much weight into general health. 3d6, 1d6 for general health, 1d6 for body mass, (durability) and 1d6 for endurance. You can measure mass and put a number on endurance. Now we are left with a somewhat healthy scale. Maybe start with 6 and subtract 1 per health issue.
So similar to the scenario above, say you just hit somebody with a solid strike. What determines if that person is still standing or conscious?
Well, those are the physical characteristics. Pretty soon we will have a CFC Questionnaire for RPG stats.
