Now I get it. I was referring to using a leather cleaner to clean up some stains on leather such as ink stains, grease, etc... For this I'd use a leather cleaner. However, it's also a good idea to use 303 on leather as it turns out periodically just to condition it up a bit and to add some UV protection. All my posts about 303 were always based on exterior trim, tires and the vinyl dash and plastic surface areas. I had only used 303 on leather seats 2 times in 15 months or so.
Anyway, as it turns out, 303 is great to use on basically everything in the interior, except for glass of course.