I remember doing number line exercises like this long before common core. This problem is relatively sensible and shows how to subtract hundreds, tens and ones and allows the students to learn through finding the errors of others. There’s a lot bad about common core, but I don’t think this problem is the place to do battle. Now if this is all that is taught, or if it is used to prevent full understanding rather than being a stepping stone then fight it.
Personally, if I were trying to solve 427-316 in my head, I too would first take off the 300, and say to myself "Okay, now it's 127-16." Then I'd take away the 6 and think "Okay, now it's 121-10," and from there I'd be okay. I think that's what they're trying to teach here.
It is just plain stupid to teach math this way.
-1 *scoffs* at you for being so gullible.
(Just wondering.)