But this does not apply when buyer is well behaved
How do you know they are a well-behaved buyer?
I think we are having a violent agreement!
That is indeed the question - who is "well behaved"?
To avoid looking like a scammer, evidence is everything, to influence the balance of probabilities your way. Being clear and well documented (pictures, videos) just works! Having a long history of buying stuff with no problems is also important!
That's why I keep banging on about the need to go above and beyond in preparing your complaint: be super clear, super well documented, lots of pictures and videos, make sure some show using the stuff on your desk / in your lab area (making you look more genuine).
At the end of the day, it is going to be a judgement call. If you didn't communicate well, or if your account is new, or if your account doesn't have a good track record of "well behaved buyer", you increase the risk of falling into either the 'scammer' or 'unreasonable idiot' category by default, because - as you correctly point out - there are a lot of scummy buyers as well as sellers!
Scams work because other people are taken in, and the only reason you think well-behaved buyers are discernible is because you are one. From the seller's perspective it's completely the opposite, and they consider well-behaved sellers to be just as obvious to buyers.
One well-known scam on Ebay is to buy, say, a motherboard to replace the one you've broken (maybe screwed over the CPU pins when doing an upgrade). Then you send your old one back pretending it's the new one and complain that the vendor has sold you bad stuff. As the Ebay rep who only sees the buyers photos and has the vendors word that it was OK when sent out, honest, who are you going to believe? The vendor more often than not loses out in those cases.
Why should Aliexpress be different? Well, obviously, it is cheaper and the shipping is peanuts out so vendors can basically give the stuff away, but it costs a fortune to return. So vendors are better off writing off stuff instead of paying for returns. Given the toerags that populate this world, and that the majority of Aliexpress customers are there precisely to save a few bob, what are the chances that they are all going to be straight-up guys?
I totally agree. Most scammers are not geniuses, though (or they would be doing something else, lol). There is a limit to how well they can keep up the charade against an opponent that's on the ball.
Hence, it can make sense to video the (un)packing of the box, showing the part numbers, showing you turning it on, etc..
I've recently had bad luck with two eBay cell phones in a row (both had internal tech issues, one was in a boot loop, the other had lost its wifi/bluetooth connectivity). I had no problems whatsoever returning these items for a full refund, with shipping paid by the seller... but I have thousands of positive feedback over 20 years, and my complaints are always straightforward, to the point, and always includes pictures.
I recall once buying a heat gun from a Chinese seller on eBay. He sent a 220V model with a US 115V plug on it... To win that case, I had to explain to both seller and eBay case managers why that idea was never going to work... There was no way to ship it back economically even if it was an "honest mistake", and there was no way for me to make use of the item. - It was a total loss for the seller, and I threw it in the recycling.