Nonsense. There's plenty of very large people who prefer little bitty sopranos. Everyone is different. But if just starting out, at 6 feet, a tenor will give you more room between the frets, and may be the way to go.
If that were true there would be far less adult soprano players as there are. I'm 6 foot and I mostly play soprano. I don't even own other sizes aside from one baritone.
Some teachers/instructors/whoever sometimes claim that you should position the uke in the crook of your arm and if your fingers are approximately at the optimal strumming position (around where the neck meets the body) the uke is the right size for you. I personally believe that's nonsense. There's no reason for the uke to reach the crook of your arm. As I said, almost no adult would play sopranos in that case. The way I hold the uke is I let my bare forearm rest on the upper side of the lower bout which creates friction between the forearm and the uke. No reason for the uke to reach the crook of my arm at all. If I'm sitting down there's even less reason to hold the uke with any part of my hand. I just let it rest on my lap.
When it comes to space for fingers, nut width (or string spacing) is usually the most common limitation. The wider the nut the more space you have between strings, and this has nothing to do with scale length. Or course with larger scales you have more space between frets but I seriously doubt anyone would struggle with space between frets unless you had really large fingers. I think it comes down more to what any one individual is used to rather than space between frets.
If you're not in lockdown and can go out to try the different sizes for yourself then start looking around for places where you can make up your own mind once it is wise to do so. If you don't have any uke specialist dealers around and you have to buy online then ask Mim's, HMS or Uke Republic for advice. Many people end up with a concert as it is the Goldilocks size. As there are not as many baritone uke channels on YouTube most new players are a bit reluctant to pick the baritone for a first ukulele, unless they already play guitar...
James Hill had a segment on this a while back. He had some exercise I think where he placed the ukulele in the crook of his arm and got some measuement that supposedly told you what uke fit you. I really like James Hill, but I think that is a bunch of hokus pokus. I don't think it makes any difference. Personal choice.
You can learn to play any size of ukulele you desire. Pick the one that sounds best according to your taste. Heck, you might like them all. All ukuleles are small compared to a guitar, bass, cello, etc., and even children with small hands can learn to play those instruments at virtuoso levels. Also, as you learn ro play, the muscles in your hand become stronger, more flexible and more dexterous. Four decades out of my teen years and my left hand is able to do stretches and positions I only dreamed of as an 18 year old. I often switch between ukulele, guitar and bass (in the same set) and the brain learns to adjust to different scale length with a few months toil.
my vote is that it is all a bunch of mummy-rot. I would have said poppy-cock, but I've been reading British novels. Your hand will adapt, if it even needs to, to whatever ukulele you decide on. So follow your heart on the ukulele you want and your hands will follow
Do only short people play violin, medium people viola, or tall people only cello or bass? If stature doesn’t determine which instrument in the violin family people play, why should it be so for the ukulele (which Crusty the Clown calls “the thinking man’s violin”)? I’m another 6 footer who prefers soprano ukes.
I am six two and play mostly soprano, from choice! I also have a sopranino which gets a lot of use. I do own two concert scale instruments and they get a fair share of playing time, but soprano would be my 'weapon of choice' as per my signature!
I always suggest a concert scale uke to a beginner - you'll end up buying more, it's just what happens - but the concert is the best starter uke in my eyes, it has a little bit more space than a soprano, &, usually, a little bit more sustain too.
I'm 6'1 and own a couple of tenors, but I've never been happy playing them. Concerts and sopranos make my hands much happier. I don't have big hands (can't reach a big 10th on the keyboard) and the uke is my first fretted instrument. When I want the "tenor" sound, my Romero Concert comes very close to it.