I think the important thing they are trying to get at with the homework is not the mental math, which is done through drills, but understanding how to explain math concepts.
The fact that many people find those extremely difficult suggests that it's necessary to teach it.
I will say that my children do math from three different countries' work books (long story) not including US math and asking them to explain, using words, why 1 + 3 > 1+ 2 is NOT unique to some stupid US math curriculum.
In fact it appears to be integral to the math curricula in the most highly-scoring countries as judged by the PISA, among other things.
So, that's just my 2c on why it might be worth it to have your child think through these easy-peasy problems. I can sing Mary Had a Little Lamb. What note does it start on? What key is it in when it starts in that note?
Math has theory just as music has theory, and it can be beautiful.
Easy? Nope. Fun for all children? Nope. But hey, this is a gifted forum, so who said the kids needed easier work?
