I've seen a lot of common core crazy **** but I don't see the problem with this one. I'm assuming they are trying to teach kids how to do arithmetic in their head, in which case the "make a 10" rule is pretty much how everyone does it. Either this or the opposite (14-10+2). That's what I was taught and it has worked out alright for me I guess.
That is exactly what all this common core crap is. The problem with it is that you need to teach a good basic foundation before you teach them the short cut. I went through this with my kids. Because I have an engineering degree I was made the ho to parent for math and science homework. I would sit down every week and goggle what they were asking for so I could then explain to my kids what they had to do. Very frustrating for both the parent and the kids.
I honestly don't remeber the addition subtraction part. The biggest one i remeber was multiplication and division. They had to break everything down into their parts and do it individually. They spent all week teaching different division techniques and had my son in tears. I told him just muscle though this crap then I'll teach you the right way. At the end of the week I sat him down and we went through traditional long division and he looks at me and says" why did they just not show us this... this much easier."
Can't tell if serious. Unless you're a youngster. Don't mean that in a mean way, but maybe you don't know their atrocious history:
Yeah I do a fair bit of math similarly (more with multiplication, but sometimes with subtraction). Breaking things down to the nearest ten can definitely make it easier in your head, at times, imo. In the end, it's just another tool for people that think in that way. Not a necessity, but an optional tool.
Maybe it isn't such a bad thing...we can't be much worse in the area.
. Just haven’t seen you post as much, of course I’ve not paid much attention. Grandmas unite! I’m gonna ride that for years. 
And nothing like those grand babies!!!