Do they really recycle the old memory chips? If you take a GPU it usually has about 8 memory chips. And its very easy to remove these chips if you have the right equipment. Heat it up for a minute or two and remove it with a suction pen. The pain will come right after.
Its very difficult and time consuming to take off the old solder and then you need to carefully apply the balls on the solder joint, you use a stencil to do this. Again this is doable however doing 8 chips will take 30-60 minutes depending on skill level. If this was reballing some GPU chip for a product worth $500 it would be worth it, but to go thru this hassle of reusing the memory chips just sounds crazy.
Yes, they do. The GDDR5 memory is dirt cheap so it might not be worth the hassle of replacing all of them. Cost and labor work to replace all of the memory chips isn't rewarding so sometimes, people sold a faulty VGA with GDDR5 memory for 10 bucks. Usually, if you got like 1 or 2 faulty GDDR5 memory, replacing 1 or 2 is right up everyone's alley.
It isn't like they need to reballing all of the memory. They just took the faulty VGAs with a few bad memory and replace them with the recycled memory that they got from other VGAs. Basically, the frankenstein VGA, you see. Some are greedy enough to retouch the PCB so it looks new and sold it with the tag as a brand-new product. GDDR6/X is now where this process is profitable while GDDR5 is less so. Thanks to the crypto mining boon back in the heyday leading to the massive amount of GDDR5 flooring the market, so you're half-right on your assessment.