That's wild, isn't the flipper basically just a TI CC1101 wireless dev board? Is Amazon going to ban every TI wireless board next?
i.e. Selling air-duster to dust things is different to selling air-duster to get high, even if it's the same product you are selling.
The root problem here is sloppy security through obscurity practices. If you use proper security like RSA certificates on NFC cards then there is no way a simple clone and replay attack (like a flipper or Android phone with NFC can do) will work, it is 100% impossible without breaking RSA encryption (which would be a lifetime achievement/Nobel prize worthy feat).
As Flipper Zero is marketed as a 'hacking tool', discusses use-cases as cloning cards and acting as a 'bad USB' device, has a indie go-go page that implies that you could use it to break into car parks, I'm not entirely surprised that Amazon wouldn't want to stock it.
This doesn't mean I don't think it's a great product - I want one and I'm glad it exists. I'm just also not entirely sure I would want to sell it if I was a global retailer.
It's probably just not been flagged to them yet.
I'm no policy maker, but I'm sure the convenience is the deciding factor. This device allows amateurs to perform a wide range of sophisticated security breaching tasks, for example.
The TI CC series of wireless chips are _decades_ old and in use with thousand and thousands of devices. You almost certainly are surrounded by multiple CCxxxx chips _right now_ in any little wireless remote control or iot gadget. These are extremely common chips and banning the flipper because it's a hacking device or whatever is just silly since it's not any more problematic than the TI CC wireless dev boards and devices.