After today's emerge-webrsync, I have found that python_targets and python_single_targets use flags have been changed again from python3_5 to python3_6, which leads to a lot of recompilation.
It already happened last month and a week later the both use flags was changed back, again with a lot of recompilations. And it was not the first time! Is any real need to switch python_targets and python_single_target back and forth every month?