I agree with the main tenet - "car wash" is clean water; road spray is crap. Dirt, oil, salt, sand, abrasives, whatever chemicals other vehicles have spilled/dripped on the roadway...
For comparison...
Would you drink out of your garden hose?
Would you drink out of the drainage ditch as its raining?
That said, I don't "wash" my (unrestored, original coatings/paint/seals) Charger with a hose, because of a) original (dried/cracking) weather seals, and b) the relatively-tattered vinyl roof (I don't want water collecting under there and starting / expanding roof rust, if possible). Just yesterday, I put a new engine harness on it and pulled it out of the garage for the first time since Carlisle. It had garage dust on it, of course, so a wet wash rag followed by a chamois to dry, and she's ready to go again.
ALL my other vehicles are rain-worthy, and wash-worthy (including motorcycles), but I do treat the Charger with kid gloves due to the seals. Eventually I may replace them, but (like my currently-inop wipers)...it's down at the bottom of the list because I try really hard not to get it "that" wet. And if I do get caught in the rain...that's what the Rain-X is for on the windshield.