I counter with the following observation: You note that a return policy exists so that customers can use it. Under what conditions are you allowed to use it and it not be abuse?
Being able to return the product is often why customers buy something. How many times have you considered the return policy before buying? You can decide to return it for any reason you like: whether you dislike the product, whether you ran out of money and needed a refund, or for no reason at all.
If it's a problem, the business will change the policy, just as Apple did here.
I'll give you an example, which is also a true story: I bought a 4K TV that could also run Android apps. But, while regular TV broadcasts displayed in 4K, the Android apps were limited to HD. This, of course were never mentioned in any of their marketing material. Did return, and did get a refund, but if it had worked as I thought it did, I would have kept it.
You claim it's okay to follow the letter of the policy and abuse it. When too many people do that the policy is removed.
Result: You live in a culture where returns are disallowed.
Me, I'd prefer to live in a culture where returns are allowed. That only happens when people don't abuse the return policy. The fact that Apple changed their policy because people abused it is a loss for everyone that had no intention of abusing it. It's even a loss for those who were abusing it if they ever have a legit reason to want to return something.
There are a many many policies that only really work on social norms. Living in a society that respects those norms is "almost" always a nicer society to live in.
I'm not sure whether there's an ethical problem with acting in that way, but it resembles a "tragedy of the commons" situation. Or, "this is why we can't have nice things".
If your plan wasn't to return it from the start, then it isn't abuse. This seems pretty simple. In your original example your "friend" was planning on using GPUs to test and then return them. At no point was he planning on keeping this purchase.
Now, I will say if you're friend bought 3 GPU's with the plan to keep one and returned two I would say that's not abuse, but there are certainly better ways to try before you buy.
I think the issue is people operating in bad faith. I recall a story about people buying big TVs before the super bowl then returning them the next week. My opinion is that's abusing a company's generous return policy. The people doing that never intended to buy. The company had the policy to give customers more confidence in their purchases, not to run a free TV rental business.
There's a saying "this is why we can't have nice things". If people constantly push leniency or generosity to the limits, they get taken away, and it's a net loss to everybody else.