Those ideas are definitely not knew. The verbiage surrounding the ideas might be new, but ideas behind the methods have existed for as long as I have been teaching elementary math (which is since the 1990s.) Young children can learn those methods very easily. I have taught them to every single one of my kids.
I personally don’t think the issue is with the concepts being taught, but in the way they are taught and trying to make simple ideas complex or asking little kids to think in terms of providing a proof vs. just letting them demonstrate that they understand what they are doing. Older kids…definitely proofs are appropriate. But little kids??