Please see point d. Specifying Amazon as the seller merchant does not mean what you think it means. Let me give an example in the form of a question / answer
a. If Amazon sells a 64 GB Sandisk card
b. Merchants A and B also sell the same card
c. Merchants A and B have opted into the fulfilled by Amazon program.
Question: You purchase the 64 GB Sandisk card and pick Amazon as the seller. Whose inventory did the card come from?
Answer: Undefined.
For semantic purposes we can think of the following mental model - For a given SKU Amazon takes the memory cards from its own inventory and inventory from all other resellers who have opted into the "Fulfilled by Amazon" program (in our example A and B) and puts it together in a giant heap in its warehouse. When a order comes in a card is picked at random from the heap and shipped out to you.
And this definitely isn't a theoretical problem. People have had countfit items delivered by Amazon.com themselves because of the comingle issue (and third party vendors suspended because a different vendor tried to sell fakes, and they got comingled).
> For a given SKU Amazon takes the memory cards from its own inventory and inventory from all other resellers who have opted into the "Fulfilled by Amazon" program
No. Sellers have to opt-in to co-mingle, so it's certainly not "all other resellers".
Besides, I think co-mingle only applies to resellers's stock, ie Amazon stock and 3rd party sellers' stock aren't put together in the same basket -- although I could be wrong about that.
They have no reason to. The idea of commingling is they can pick the best warehouse to ship from when a customer orders instead of (potentially) shipping across the country. They actually like commingling because it helps their logistics.
Generally Sandisk items are restricted, i.e. only authorized resellers are allowed to list them on amazon. (There's also a $1000 fee payable to Amazon to be allowed to sell them.)
So for Sandisk specifically this isn't a concern, although your comment applies to other, unrestricted brands.
98% positive and 2250 lifetime feedback ratings means it's probably a good seller, just not authorized for sandisk and listed there to get around the rules. If someone took the time to report them the listing would be removed.
OTOH the same seller lists https://www.amazon.com/dp/B00M55C0VU, which I've confirmed on my account is restricted. So maybe they are authorized, and just listing on any ASIN they can find that matches the product? I've done that sometimes.
It doesn't look like customers are being harmed in this particular case, it's possible some unauthorized seller created the listing and VP distributor simply jumped on it at a later point, the first seller could be suspended now.
There's a d., the seller has to agree to co-mingle their inventory. Which a lot don't, since that means they can get dinged by another 3rd party's bad inventory....
a. If Amazon sells a 64 GB Sandisk card
b. Merchants A and B also sell the same card
c. Merchants A and B have opted into the fulfilled by Amazon program.
Question: You purchase the 64 GB Sandisk card and pick Amazon as the seller. Whose inventory did the card come from?
Answer: Undefined.
For semantic purposes we can think of the following mental model - For a given SKU Amazon takes the memory cards from its own inventory and inventory from all other resellers who have opted into the "Fulfilled by Amazon" program (in our example A and B) and puts it together in a giant heap in its warehouse. When a order comes in a card is picked at random from the heap and shipped out to you.