[combat] giant issue in weapon reach question

[Ji ji]

Hello everybody. I'm Ji ji, role-player from Italy.

I started playing GURPS twenty years ago. Recently I approached 4th edition, and I like the great improvement in the rules, which I already liked in 3rd. With this new edition I passed to tactical combat rules, in order to obtain a greater degree of realism.
Yet, it seems to me that there is a big issue related to combat mechanics (as a simulation) regarding weapon of different reach. I was asking myself if I miss some paragraph and misunderstood overall mechanics.

In my experience, with the right condition, greatest reach give enormous advantages. If we are in open space (for instance, in game terms, a 10x10 grid without any obstacle), a spear is often superior to a shortest sword. In such situation, a spear-armed warrior defeat a knife-armed one 9 on 10, or so. It's similar with a long rapier vs short-sword, and so on.
But this is the less issue. The big it's combat dynamism. In real world, if you look this combat, you see much more attack coming from spear. The shorter weapon wielder will do a lot of parries, and his biggest effort will be enter in the other's guard, going enough close to attack.

In GURPS I see a far excessive mobility, an excessive ease to close to the opponent. I do a pratical example.

A and B have the same physical stastic, but B is slightly healtier (12 instead of 11). So, B has an higher basic move and act first. They are equally trained in martial arts; A is a spear expert, B a knife expert.
They start the fight with two meters (two hexs) between them. A is wielding the spear with a 2-reach grip.
B go first. His action is "wait: if he closes, I step and attack".
Now A make a step to attack. B make a step and attack. With the first parry in a turn, probably they parry both.

Now A and B are in adjacent hexs. B attacks. A must change grip, using the ready action!

This is a very bad simulation. Regardless this specific example, it's far too easy to close distance in combat! The best tactic to take advantage from longer reach weapons is to go forward, and this is very irrealistic. In a real fight, longer weapon wielder can easy mantain his position, keeping shorter weapon wielder at distance. I can't see how simulate this in GURPS combat. Worst, the above strategy is impossible if A has a wall at his back (in real, a wall at back is a great defense).

Is this inability to keep at bay the opponent a real (giant) issue of combat mechanics, or I miss something in tactical overlook of the rules?