The whole thing sounded a little like a bit of buyer's remorse. But not sure what else is missing from the story.
I feel that the SA has a responsibility to be clear on the return policy before a customer buys. If there are no returns on these items, it needs to be explained before the purchase is made. Even if this guy buys a lot of LV, it doesn't mean he knew better.
As a customer, before you spend thousands on a watch, be sure you really love it. If it was too heavy I would think this was something he would have noticed when he tried it on in the store, and removing a link or two won't make much difference.
At the end of the day he was really fortunate to get the credit, which sounds like he would have no problem spending on other things. Not sure why he pushed for the full refund unless there is a financial motivation for him (regret spending so much or wanted to use it towards some other watch).