Good Question....
Here is my long opinion on the subject....
I've been asking my self the same exact thing for a while, mostly because I can endure some strong motion and VRT exercises, while sometimes even sittign down I could be really off...
I think, from what subs says that VRT is designed to match, or compensate for the everyday motion, helping the brain to "learn" again all of what it forgot because of the injury.
This learning process is not so quick, and it it's different from person to person, because of it's injuty, age, general condition and many other factors involved.
My catch on this is that it do helps, but when you're decompensated by something, MAV factor, allergies, colds, there is a new imput wich has to be learned and somehow "confuses" the brain for a while, or more in the case of MAV, keeping it off, even with the help of VRT.
The psychological aspect of it all may be tampering the overall feeling, because, at least in my case, sometimes doing VRT reminds me that I'm ill, and this gives me an extra emotional weight to deal with, and in the event of a decompensation, even if it's a mild one this weight can be deppresive, not because of the decomp itself but because of what we all add to it, thinking, "Oh no, here I go again!".
There is a point, as you may experienced, where exernal factors such as a "do or die" situation or somehting htat keeps your mind off the dizziness, kind of "connect" some mechanism where you don't feel off, or at least it doesn't affect you whatsoever.
But in a constant worry state, even some mild symptom wich could pass unnoticed in another situation, could easily give us hell, and I think this could affect recovery and compensation both in an objective and subjective way.
Finally I believe that VRT will help you to pintpoint some specific stuff that your brain "forgot" wich could take even more time to put together without it, slowly but surely, but the attitude helps, this is why doctors said that you shoul choose some exercises or activities(aside from VRT) that you enjoy, you don't need to suffer your workout.
Obviously, in all cases you must detect and attack any decompensation factor wich may be tampering your recovery and minimizing the benefits of VRT altogether, like in my case I'm dealing with allergies, wich eihter are on the rise here in Mexico City, or I'm paying more attention to them(this is kind the "worry" state), because more and more people seems to be affected by them, and with my vestibular trouble added, I'm quite off lately, aside from this I've experienced some MAV like symptoms, an due to my migraine history this could be a tampering factor too.
I'm trying to figure out wich one is the main problem, or in what amount each factor affects my recovery, because some days I can reach a strong 99.9% with no change in my routine whatsoever, and some days I went down hard, even with VRT and stuff.
Nevertheless I try to keep on VRT altogehter, challenging my brain to learn it all again, and sometimes "forcing" my self to keep it up, even in a decomp, trying to make my body adjust to all the changes without dizziness in the future.
