Oh gotcha.I just heard it could make cycling your tank take longer but I don’t know if there is any truth to it or not, that’s why I was wondering if that has any marit or not
Nah the only reason why that would slow down a cycle is if it removed enough ammonia/nitrite from the water that you would not be experiencing enough growth of nitrifiers, but that is not really a concern because re-introducing ammonia (and nitrite) again would be easy.
The other way is if you accidentally change water that had some issues, like hypo- or hyper-salinity, or full of antibiotics or whatever, but of course that's not an issue with water changes during the cycle in and of itself.
So moving on, what a 100% water change does is to remove as much of what is actively antagonizing your live stock in the water as possible. Whether that 'clears' everything right away is not something absolutely ascertainable, but either way if there is something in the water that is irritating your live stock, at least most of that would be removed for now.