I just recently had to do some research on leather and ran into some interesting info.
Apparently today's leather in US & Japanese automobiles is covered by a plastic coating.
Interesting read on the 303 website and it cites comments made by a Dr. Jenkins of Lexol
303 Products, Inc.: Treating Leather and vinyl coated leather in auto upholstery and car interiors.
From the article
“
While vinyl-coated leather is care free by virtue of its protective plastic surface, it is also inaccessible for purposes of maintenance.” Meaning, of course, there is absolutely no point to using leather conditioners on plastic coated leather."
The water drop test tends to make sense. If you put a drop of water on a solid leather seat that isn't perferated or not on the seams and it doesn't soak in, it would stand to reason that a leather conditioner isn't going to soak in either.
If that's the case, then it would seem reasonable to think a vinyl/plastic treatment would do more good than a leather treatment if your seats are plastic coated.