I have two Macs, a Macbook Pro Late 2015 with a 2,7GHz i5 and a Hackintosh with a 3,3GHZ i5. I cannot see any effect on the CPU, the meter does not show any changes when I use Ableton with Push. I can´t reproduce any of the issues that are mentioned in this thread although my machines are less powerful. Seems to be an error due to the overall configuration of their systems.
[edit] I further read through this thread at Ableton forums, people there seem to be lost using OSX´s activity control program. “90%” CPU usage means 90% of the current cpu usage . If your overall cpu usage is at 10% and Push 2 uses 90% Push is using 1% of the WHOLE Cpu power, not 90%.