I can vouch for it being very effective at cleaning tire sidewalls, especially if/when you don't want to drag out the hose and get the floor wet. I've seen Nick clean the tires with either M39 or M40 just about everytime I've been to TNOG.
Those shiny cars you see in the pics aren't done until Nick puts the finishing touch on them, and that means making sure the tires look good to match the paint. M39 spray and wipe clean. I think I can speak for him and say he really loves that stuff!
IMO 1 of the benefits of M39 is that it's strong enough to clean like a degreaser, but it checks all the boxes in terms of doing it safely on all the intended surfaces. Meaning it won't turn certain rubber/plastics chalky white like Degreaser can sometimes do on certain areas.