This is really interesting...someone should get down to the underlying chemistry that's going on here.
It seems like the question is: are the cleaners removing brown residue from rubber that was already oxidized (which they should be doing), or are they causing the oxidation themselves (which would cause premature drying of the rubber)? The same thing could be asked of the dressings being used.
I'm no chemist, but here are my thoughts (on how the cleaners and dressings could cause premature wear/drying out/browning):
1. What if the dressings/cleaners (or a byproduct thereof) are absorbed by the rubber, and form a barrier that the antiozonants can't penetrate, therefore keeping them from getting to the surface of the rubber where they need to be in order to be effective? (The more I think about this, the less it holds up.)
2. What if the dressings/cleaners somehow react with the antiozonants and incapacitate them, keeping them from performing their function? (I haven't thought this part through yet, so I'm not sure if it's even chemically possible.)
However, since the browning is basically oxidation of the rubber, don't the dressings act as a barrier between the air and the rubber, which should help to inhibit browning?
What if someone tried to contact one of the tire manufacturers? I know this is a little "out there", but maybe they could help shed some light on the issue? I mean, after all, they did formulate the tires!
What I'd suggest for a good experiment (to test the dressings' effect on tire browning), is for someone to only use tire dressing on one side of the car (yeah, it'd look pretty ridiculous, but this eliminates a few degrees of freedom, namely the variance in browning front-to-back due to varying degrees of sidewall flex and the way debris is thrown up into te air, and if it's done on the same car, eliminates variances due to different driving conditions and tire brands/rubber compositions). Then you could compare the browning of the side with dressing, to the side without, and determine if the dressing caused additional browning, or protected against it. You'd just need to make sure the tires were all evenly cleaned prior to te start of the "test". (I know the obvious suggestion is "well, why don't YOU try it?" Well, I'm not ready to tackle such a task. My car has rarely even been washed (if at all) since winter started. So maybe someone in a warmer climate with a little spare time on their hands would be so kind as to give this a shot?
As far as testing the cleaners, I'd say you should stay your course on this one, and keep trying different cleaners on the same tires, and see how the tires look afterwards, going off the assumption that if a tire ends up more brown than it was initially (assuming it wasn't dressed, or the dressing had worn off), then the cleaner can be assumed to be causing the oxidation.
Personally, my method for cleaning tires is:
I'll spray the tires down with Greased Lightning Orange Blast (full strength, I know it sounds like an aggressive approach) once every 3 car washes or so. I'll let it sit for a minute or so, then scrub with a brush and rinse (resulting in a nice brown residue normally), taking care through the process not to get any cleaner on my wheels. I'll then follow this up by washing the tires and wheels with
Meguiar's Gold Class soap at 2x the suggested concentration, with the thought that it'll help to counteract the drying-out effect that Orange Blast seems to have, and restore some moisture to the tires (this step does seem to help restore the black color that Orange Blast sometimes takes away). The 2/3 of the time that I don't use the Orange Blast, I just skip that step and go straight to the GC wash.