Except it isn't - 8GB boards that started their lives as 1/2GB variants are absolutely on the market.

>but given how few users are actually capable of doing this upgrade, also probably an imaginary problem.

Just remember that in China there are places where you can get your iPhone storage upgraded by someone desoldering the original chip and soldering on a new one, they get the whole process done in 20 minutes. If labour is cheap and the skills high that's what you get.