They kept referring to it as a time alteration, but from their description, it basically makes something briefly invisible. But we can already do this... so what's the big deal? Just another method?
It's both very analogous and very different.
A normal 'cloak' hides a region of space. That means as you look in a particular direction, the light is bent around that region in such a way as to not give you any information about it. Say that region of space contains some object. At every point in time, as you look in a particular direction, you get an image of everything
except that object. It's cloaked. There are no holes in the image itself; the object is simply not part of the image because of the way the light is manipulated.
A temporal 'cloak' hides a region of time. Once again, say that region contains some object--to keep things simple, imagine a little mechanical counter that counts out the seconds seconds: 1,2,3,... The temporal cloak manipulates the light in such a way as to always give you an image of clock, but hides a certain time interval. For example, as you look at the image of the counter, you may see:
... 97, 98, 99, 100, 221, 222, 223, ...
There's no discontinuity the image you see; you always see the clock. The image doesn't hang at 120 seconds until the counter gets from 100 and 221. That time interval simply isn't part of the image anymore--to you, it looks like the counter went directly from 100 to 221 in one second, despite the fact that it was physically there, counting all the intermediate steps.
(That's a
far exaggeration of the scale of their temporal cloak, but it is the same kind of thing in principle.)
