The problem is the fact that you are able to summon an entity with the same UUID as others, causing various glitches. This could be a problem if you summon a mob with the uuid of 12345678-1234-1234-1234-123456789123, and there is a mob already with that uuid, then it could potentially corrupt your world ( has happened )
but you can give yourself the spawner with the NBT as a item.
I have used the article, and now have changed the description. If this is still too difficult to comprehend, then please tell me so I'll attach a video, which is limited from my grasp at the moment.
I was on a super flat at night with scoreboard and fast clocks on testfor for an entity. I would make a 3 block tall wall and then I would go into spectator mode. While no-clipping inside of the block I would change into creative witch would make you suffocate. Then you could destroy the 2 bottom blocks and you can not move, unless you jump frantically. I've reproduced this on a clean jar with the snapshot. No resource packs ect.
Yes, There At The Same UUID, Because The [UUID] Test Works for Testfor / Tp ect
to have a message saying "UUID Already being used" or something.