So how can this be verified to be genuine WD drives or not?
OT: I've also seen some Intel NIC's that's stated as "original" like this one from 2013:
https://www.aliexpress.com/item/1005004075383590.html
How much trust can be put in these sellers?
In today's market, it's extremely tough if not impossible. Back when I ran into a batch of 'genuine new' Intel NICs, I was able to call Intel and they were able to figure out from the numbers on the box that they were not genuine because the numbers while valid (including the serial number), did not all correlate the way they should. They were able to confirm that the driver CD was genuine however. And this was nearly 10yrs ago. Today's scammers have become very sophisticated, duplicating almost everything in exact detail to the point that the only one that will know the difference is the manufacturer. And that puts us the buyer in a very tricky situation. The only solution I have found is if you're buying new, buy from sources that are 100% legit, starting with the original manufacturer if possible, or get genuine used items from recyclers (even thought I've gotten a pair of fake xeons this way, so even this isn't foolproof).
As far as trust in sellers--none except when they are known to be legit, and definitely none if they're shipping internationally from the third world. Otherwise, treat them as some guy on a street corner with a long trenchcoat asking if you want to buy a watch...