This is why so many external USB battery packs for phones and the like have a flashlight built in - it's a legal loophole that lets the manufacturer pretend it's a flashlight, and not a "raw" battery.
Interesting. Although I actually find it useful that they include the flashlight. Win/win.
Because the risk of a mechanical accident damaging the battery is smaller. Also less similar batteries in close proximity to catch fire
This is not quite right, but once a 'small' single cell is in a 'package', shipping it with other similar products is only subject to the 'overpack' rules.
Some companies still prefer to err on the side of caution, every single device I have ever ordered from T-Mobile has had the lithium sticker on the shipping box even though as far as I'm aware it's not required (especially in devices with non-removable batteries).
Are you sure about this? Lenovo, Dell and Acer all put big LiIon warning/danger stickers on their laptop boxes when shipping. Are they doing this voluntarily?
Some of the batteries are removable, but others aren't. Maybe it's related to the size/capacity of the batteries?
IIRC there's a legal limit on the allowed capacity of a Li-ion battery in a device on an airplane, yes. That might be related.
So just put another box around the battery and call it a battery-powered box.