If there are fish in the tank them waterchanges are a must, doing so will slow down the cycling process to a degree, but you cannot leave your fish sitting in that water.

If you are doing a fishless cycle waterchanges are not required, once the tank is showing no ammonia & no nitrites, and only nitrate, then you do a water change as it has completed the cycle and fish are safe to slowly add once the waterchange has dropped the nitrates.

Its not that you remove bacteria when waterchanging, you are removing their food source which IS in the water column, this is what slows down the cycling process. Fishless cycling is a quicker way of cycling a tank.