It's the same for FPS at high level. Learn the map and the probably position for anytime at anytime.
They don't spend a lot of time aiming and moving when already knowing where the enemy will show up. Just have to click.
To give a good illustration, top players could almost play blindfolded.
Yes, there are tactical positions, but you can't just camp for most of them. They maps are large enough that your team must be dynamic enough to adapt.
You also can't just click without aiming. Damaging a tank always requires aiming, even if you know where they may show up. Many tanks can only be damaged effectively in small weak areas, depending on the gun of your own tank. This can require that you actually focus for several seconds on the spot you are trying to hit to get a good enough aim to actually hit it.
Due to the game mechanics of 'aim time' this somewhat eliminates the huge advantages of ping time and those with super human reaction times.
Doing well requires good team strategy as well as deep understandings of tank mechanics such as armor weak spots, tank positioning to increase chances of bounces etc and also map strategy.
Therefore, the great players aren't those who have developed better reaction times, they are the ones who have developed deep knowledge and skill around the games many maps and 300+ tanks