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
5Dmk3, 5Dmk2, Sony NEX-6 | SY14mm f/2.8, Ʃ20mm f/1.8, 35mm f/2, Ʃ35mm f/1.4A, 50mm f/1.8 I, Ʃ50mm f/1.4 EX, 100mm f/2.8L Macro, 17-40L, 24-105L, 70-200 f/2.8L IS II, 1.4x II, 70-300L, 100-400L | E-mount: 16-50 OSS, Ʃ30mm f/2.8 EX DN, 55-210 OSS | 2x FT-QL, AE-1 Program, some FD(n) & FL primes