Of course there are other differences.
I was just pointing out a big problem that the majority of adults face and why their progress is extremely slow.
There are other factors aswell.
A few of factors kids just have the advantage naturaly, but in others they dont but still get more than most adults out of it because of circumstances.
Heres a few:
1.Kids are still learning to walk, move, run etc... adults are done learning, so kids brain absorb movement and coordination like a sponge at like 6-10, while adults or even 16year olds have aleady learned that and brain has been wired for that, so teaching kids specific tennis movement and footwork and coordination is extremely easy, but its extremely hard to teach older people, even as young as 16 because their brain has been wired and learned to move/coordinate movements a certain way.
Kids have a MAJOR advantage here, older people can still learn and improve it, but MUCH slower.
My coach says it might take an adult 10 years to learn some resemblence of movement and coordination of those who started to play as kids.
2. Kids learn new things or movement differently and easier, because they have a bigger imagination and they often imagine silly things like swating a fly when learning some specific technique movement, while adults dont and not only that, adults often question if its right and doubt it and overanalyze things and get extremely detailed about every tiny thing and if they are doing it 100% the same 100% of the time.
Again kids have some advantage here but it depends also on the person, some adults are much more suseptible to this while others are less and also have more imaginitive ways of learning and also trust and do whatever the coach says.
3.Adults lack money and time compared to kids and juniors (whos parents have money and time they have unlimited amount).
Without getting too much in detail, kids simply train, have more coaching and play more than pretty much all adults so its normal they progress faster.
And their tennis time is MUCH MUCH more, than any adult, no doubt about it.
4hours per day 6 days per week, private coaching, group coaching, sparring, practice, drills, match play, tournaments
Lets be real, not a single adult in the world will come close to matching this unless rich, with all the time in the world and obsessed about becoming a good tennis player
Kids dont have a natural advantage here, but they simply get more from this
4.Adults are not patient, most adults are not patient enough to risk wins to risk playing to really learn fundamentals and basics upon which they can build, hence most coaches opt for some compromise where they get results faster but at the cost of the end goal, if you really want to become great at something you need a good fundation to build on first, start extremely slow, with boring repetitions and boring drills for months and months without even hitting a ball almost, and building a player very slowly, its a long process, kids go through it, kids start learning footwork, basic shadow swings and learning fundamentals and technique and then slowly basket feeds... it takes a long long time when kids have so good fundamentals and basics that they start playing matches tournaments etc..
Again almost no adult will ever do this or go over this slow boring repetitive process and not even play matches or hit with friends
Kids again dont have a natural advantage here but again they get much more out of it than pretty much any adult because they simply dont have the patience for it
I think
@Toby14 is someone who went through it, perhaps he can say smt about it, but 99.999% adults wont because they dont have the patience for it
There are some others aswell... but i typed too much already, my poor fingers