Well, I’m all in favor of more classes, but…
Monks always were supernatural to some extent. And they usually are so outside D&D. The specific choice of psionic power was, initially, weird, but Psionic Power made things pretty cool.
In fact, one could very possibly say the opposite: in real life, only in specific orders monks are trained in martial arts, and their spiritual side is there too. The rest are just… monks.
D&D monk has never been anything but a martial artists expert though they arent Friar Tuck.
Martial power… Let’s be honest, barring some few exceptional powers, they were nothing supernatural or even superhuman.
I actually think that is an error sure nothing supernatural that is correct but superhuman well they really should be allowed to be exactly CAS it/ought to be in there...
http://tvtropes.org/pmwiki/pmwiki.php/Main/CharlesAtlasSuperpower
Batman is exactly in there and so should be the D&D martial classes.
The line at the end of the above page --> Note this doesn't count for characters with strength from Supernatural, technological or Alien origin, but for characters who obtain this strength naturally.
tvtropes does differentiate a difference between eastern and western flavors in that the eastern ones are allowed to go over the line...
Based on the D&D monk of 1e it was a western interpretation of the eastern martial artist monastics.
I am looking at the original D&D monk below and wondering why it wouldn't be far more martial than anything else. Abilities were very subtle calling most of them supernatural would make every Martial class in 4e supernatural
Monk
The monk belongs to a religious order seeking for physical and mental perfection. The monk is a combat
expert, though he does not depend on weapons or armour. Instead, the light-footed monk uses only his fists in combat and prefers to evade enemy attacks instead of blocking them.
Special abilities
Unarmed Strike, Evasion, Danger Sense (alertness), Thief Skills, Weapon Expert
Speak with Animals (subtle almost magical but in Tolkein, dwarves and rangers did this too animal languages were something one could learn)
ESP Resistance ( strong will stuff), Slow Fall (or is it reduced damage from falling due to acrobatic ability)
Immunity to Diseases (tough guy trope not magic), Immunity to Haste and Slow(strong will)
Feign Death (ummm bluff and Feign Death practice)
Self-Healing (all over in the Martial Classes if this is supernatural they already are)
Speak with Plants (arguably the first truly supernatural thing on the list)
Charm Resistance (more strong will stuff)
Shielded Mind (more strong will stuff)
Poison Immunity (a bit of heroic mind over body you can call it supernatural if you want but... )
Immunity to Quest and Geas(more strong will stuff)
Quivering Palm (The highest level thing and still entirely explainable without magic)
LOOKS like a Martial class to me.