I was told by Dr Parihar that it's a really bad idea to do a double osteotomy outside of specific instances where it is necessary in a bone deformity case (such as when the bone is bowed). It's easier to get ballerina foot with the double cut method, and if you are one of the unlucky ones who has bad bone regeneration, your poor healing will be in two places instead of just one. He also said it's almost always the case that one osteotomy site will heal before the other, meaning you're not going to be healing faster than someone with a single osteotomy. He even said that there have been studies showing the double cut method doesn't result in any statistically significant speed up in recovery time compared to a single cut osteotomy.
The Beijing institute experimented with the double cut method back around 2008 (?) I believe, but stopped using it due to the increase of complications present in their patients.