On test strips specifically, most manufacturers (if not all?) make a specific package just for medicare and medicaid. It's meant for distribution to nursing homes and skilled nursing facilities. It is identical to the retail strips except for a few things - The package part of the NDC is different (something like xxxxx-xxxx-23 instead of xxxxx-xxxx-50) and the package has that little disclaimer about not being for sale.
The seller on amazon likely orders them based on the NDC or UPC which in itself gives no indication they are the medicare/medicaid packages, and possibly does not understand there is a difference. You might want to alert the seller so they can purchase the proper packages. Strange thing is, the cost from the manufacturer is the same for both IIRC (We've had a mixup similar to this in the pharmacy). In our case, neither our software nor our supplier has any indication in the item information that the medicare one is the medicare one.
Unless, of course, the seller snatched them from old people. In which case you should report them to Amazon.