I like the race car example from above. It just keeps things moving and may aid in more active flushing of the metabolic byproducts in your muscles.
I also like it for the mental aspect. When I complete an intense VO2 workout I like the mental cool down of just spinning and letting my adrenaline, breathing, HR, etc get back to normal before trying to go upstairs and do normal life stuff.
I also think it is similar to post workout fueling. The sooner you have a workout following then the more important the cooldown is. So if you bike in the morning then run in the afternoon it may be more important to spin out your legs but if you don’t do a hard workout again for a day or so then it’s less important.