Going to try to give some kind of answer to this using just The Unifying Force as there are so many books in the Vong series and most of the points relevant to this question will be found here anyway.
Using the Force to manipulate the air around Harrar
The most likely explanation is that Luke isn't going to directly move Harrar using the Force, but that he will move the air around him thereby moving him by proxy. You gave an example of something similar to this happening in the question with your quote from Edge of Victory.
Tahiri does something similar later in The Unifying Force:
All at once, Nom Anor could feel small Tahiri's body tense against
his. He pivoted in time to see Tahiri throw up her hands in some sort of
Force gesture, and a dozen warriors hit the ground as if struck by a
swarm of invisible thud bugs.
A Force Wall! Nom Anor thought. Tahiri used her Jedi powers a
second time to create an even wider circle of clear space
, then whirled
and grabbed Nom Anor by the arm, spinning him around to face her, her
eyes already wide with discovery.
The Unifying Force
Luke himself uses the Force to affect the Vong indirectly when he creates an energy net to kill one:
From Luke's left hand gathered a blinding tangle of energy
manipulated into being by the raw power of the Force. As if hitting an
invisible wall, the warrior stopped short, then spasmed as green sparks
began to coruscate around him.
The Unifying Force
Both of these examples show that the force can stop a Vong despite their invisibility to the Force, Force effects will affect them, they just cannot be manipulated directly.
Luke is never shown to affect the Vong directly despite having running battle to the chamber of Supreme Overlord Shimrra and a battle in the chamber itself, where he had many opportunities to use the Force directly against the Vong.
HOWEVER
Jaina is unable to move a number of Vong bodies that have buried her
Buried under half a dozen blood-smeared bodies when the bunker had
shifted, Jaina used what little maneuvering space she had to avoid
amphistaff fangs and venom, the serrated edges of coufees, and the
sharpened teeth and hardened elbows and knees of warriors. Out of sheer
desperation she tried to use the Force to throw everyone off her, and was
bewildered when the crushing weight of the warriors abated-or at least
until she realized that the sudden turnabout had nothing to do with the
Force.
The Unifying Force
There could be a few explanations for this:
- Jaina did not think to move the air between her and the bodies up, she has been in a big fight and might not be thinking clearly.
- Inconsistent writing.
- Both Tahiri and Luke have been affected and changed by Vong biotech whereas Jaina had not. Tahiri had various biotech attached to her as they tried to transform her into a Vong and Luke was affected by the venom of an Amphistaff.
While Jacen had been successful at neutralizing most of the venom
delivered by Shimrra's amphistaff, Luke knew that he was not yet
completely healed, and might never be. His body was gaining strength
daily, and he was able to keep up with his nephew and Harrar on the
undulating path, but his physiology had been altered by the venom, and he
was compelled to draw subtly on the Force to sustain himself.
The Unifying Force
Luke is slowly gaining a new understanding of the Force
A second, more tenuous theory could be with the whole "Luke (and the rest of the NJO) is not using the Force to it's full potential" aspect that is mentioned throughout a lot of the series.
Vergere, who had willingly spent fifty years among the Yuuzhan
Vong, had maintained that the seeming invisibility of the Yuuzhan Vong
owed not to any inherent failure of the Force, but to the way Luke and
his fellow Jedi perceived the Force. The implication was they had somehow
failed to grasp that the Force was grander and more far reaching than
they understood it to be.
Luke could accept that. His training had been rushed; and with the
deaths of Obi-Wan and Yoda he had been obliged largely to pursue his own
counsel, and find his own way to mastery. He would have been the first to
admit that his understanding of the Force might be limited or incomplete;
that he had perhaps become more a Master of the Living Force than what
the late Vergere had called the Unifying Force.
The Unifying Force
It could be that as Luke is beginning to believe in this philosophy and understand the Unifying Force a bit more he is able to affect the Vong in some ways even though they remain invisible to him.
