It does if you don't wipe the excess off. Stinky stuff if he's using synthetic. I might start using gear oil again, but I like a spray to clean off the chain first and have just been using a cheap Walmart brand of WD40 to clean the dirt off as well as lube it. My chain rusted after I got it wet but nobody else seems to have had that problem. Maybe I need to switch chain lubes too.
WD40 is a HORRIBLE lubricant in general, it is better than nothing but not much. It is way to light to for use as a chain lube, it is EXPECTED that you would get really short chain and sprocket life using that. WD40 means WATER DISPLACER, and was not designed as a lubricant. Many people started using it incorrectly as a lubricant because it was easy and looked clean, and the rest of the monkeys followed suit to propagate a bad idea.
Chain lube is generally pretty bad, as MARKETING is their primary goal, making it totally clean and pretty looking, with good lubrication being second. So chain lube lubrication properties are not that great.
If you want your chain to last a long time, use thick gear oil or grease. Its not all pretty and clean, but it will protect your chain very well and make it last a lot longer.