You know, I did notice this when I started channeling for my indoor Depot access, and thought to myself, "My god, this is a fucking idiotic feature!". Until I realized that, actually, it's not quite as bad as I had originally thought.
This new method of channeling makes it a lot harder for your stupid dorfs to wind up trapping themselves, because they automatically dig themselves out by leaving a ramp. When you no longer require a ramp (such as if you make it two lanes wide), it automatically removes them.
It is, however, still possible to trap your dwarves (because I did it), depending on *how* you build your channels.
As someone else mentioned earlier in the thread: ramps are built to face a single direction (at least, in regards to the channeling, it seems). So if you're channeling, dig from the OUTSIDE, work your way in. True, it becomes slightly more difficult to trap enemies (though far from impossible), but on the other hand, it can also give you a slightly better line of defense used properly.
Also, if you dig out the wall where the ramp is facing, you eliminate its support, so you are now stuck with a 'ramp' that no one (including your miners) can use, unfortunately, which is one thing I wish that could be fixed.
Yes, it is an odd function, but on the other hand, it makes strip mining a hell of a lot safer, and I think that was the main intention here, so to me it is a welcome change.