That does not limit it to mobile devices only so is missing the point.
There is no technical way for a server to prevent POW from being used with any capable device, even pencil and paper.
To claim otherwise is a scam. If it's POW it's not mobile only and if it's mobile only it's not POW. Whether it's worth it is up to you.
Exactly. That's my point. You can mine XMG on any device easily. Of course, it's not marketed as a mobile-only PoW coin. But you can easily get on-board with any mobile device unlike its competitors. Servers and/or big mining farms will still be able to mine Magi, but they'll receive a lower block reward than the "little guy".
Based on what I've read and seen, I don't think it's worth mining ORE on a mobile device. It looks just like Electroneum (ETN). As with any PoW cryptocurrency, don't expect to get rich mining with low-powered devices. Who's to say you can't have fun doing so?