It may depend on the body....
I wondered about that. And the only body I have right now is the eos-M, so it does do quite a bit of back & forth. When I had another 70-200 in the past (used with SLRs of course, mostly 40d & 50d) there was not so much "indecision" on the part of the camera.
There you go, the 'indecision' is the cause, just as is the case with my 70-200 on the 5D2
5D3, 5D2, Sony α6000, G16 | EF: SY14/2.8, V20/3.5, 28/2.8 IS, Ʃ35/1.4, 50/1.8, Ʃ50/1.4 EX, 100/2.8L IS Macro, 16-35/4L IS, 24-105/4L IS, 70-200/2.8L IS II, 1.4x II, 2.0x III, 70-300L IS, T28-300 Di VC PZD, Ʃ150-600 DG OS HSM S | E: SY12/2, 35/1.8 OSS, 16-70 ZA OSS, 55-210 OSS, SY300/6.3 ED UMC CS