Locksmith here.
On the design and engineering side this is very cool. A neat and only mildly hazardous setup.
But it's a solution looking for a problem. I can't think of any major use-cases for this kind of tool. There are some very edge-case applications. Like i need to get a key for my bike lock to a friend for the weekend but the local lock shop that can make dimple keys is closed for the weekend and I need to keep my copy of the bike lock because of reasons and… where was I?
My point is there's no legitimate reason I can think of to need to duplicate a temporary key in this way. Why would a person be so prepared that they have a pocket cast for keys but not have any extra keys?
However, I can think of a number of reasons why someone would want to be able to make a rogue copy of a key without the originator knowing. None of them are good. This would also be a handy way to make a copy of a highly restricted key blank, something that usually needs a signature and an identity card to duplicate. But those systems exist in order to maintain key and lock security. And with LPL being as popular as he is, this brings increased awareness to a method that I'd wager relatively few people were aware of before.
I doubt LPL will catch any real trouble for this, but it's not good. Teaching people how to pick locks, hell, even selling lock picks, is a real "meh" type of thing. Unless they're faced with a crappy cheap lock, most people will have to spend at least a few minutes working at picking a lock. If that lock is on a house, that's a few minutes they can't afford to spend lurking on a doorstep. But this? Making it easy to cast stealth keys? To me that's in the same troublesome realm as GPS tracking apps and smoke detector cameras. It'll mostly benefit those up to something screwy.
Although I guess if someone wears a decoder ring, writes with invisible ink, and keeps throwing stars hidden on their person, this will be the coolest thing since sliced cyphers.