I don’t believe kaihp’s lost was intended to show photos which can not be taken with a canon camera, but rather to show photos which can be taken with a Sony a9 camera. Those are not mutually exclusive.
The initial question was about whether the spec sheet frame rate of the a9 is legitimate. A single photo can not substantiate that.
I shoot with an A9, and although I haven't done my own tests regarding its performance, imaging resource has done comprehensive tests with both cameras.
The A9 can hit 20fps. But there are caveats as certain older Sony lenses are limited to 15fps and uncompressed RAW drops to 12fps or so. The mechanical shutter is limited to 5fps so that would include any flash related work. The buffer is deep, but buffer clearing is slow for JPEGS.
The 1DX2 OTOH can reach 14fps consistently in all modes. Canon advertises 16fps in LV with af/ae locked, but it seems they were only able to reach 14.3fps. Flash sync is available at the 14fps. The buffer also clears faster and is deeper than the Sony.
Yet this is only 1 comparison metric, and there are a ton of other differences between the two including a fairly large price differential between these two cameras ($2400 difference CAD in my local area). You have to weigh those differences in its entirety and decide its relevance to your work. I don't think the A9 can entirely replace a 1DX2, especially if you consider Canon's lens ecosystem, but Canon has been in the sports flagship game for a VERY long time, and I wouldn't be surprised to see remaining gaps to narrow substantially given how much was progress was made with the A9.