I will start with the disclaimer that I do not use stop bath, I use straight cold water from a tap and that is good enough for me and what I'm doing.I am just shooting for fun, and yes my negatives are all over the place, dark, light, thin, purple, but I really don't care as long as I can get a print from them I'm happy.
If you truly want to have consistent results you need to remove as many variables as you can. That includes maintaining temperature, using the same water for everything, and keeping track of all times. Yes it is easy to get images to show up on a negative, but to get them to show up the same way every time takes a lot of precise control. You can use straight water as a stop bath, and still maintain this control, but you will need a lot of it and you will have to keep it in a tank, and when the tank is empty and you refill it your results may change and you will have to adjust for that. Unless you have a water treatment set up at your home that can ensure that your water is the same every time, or you don't care about things being the same every time, use the stop bath and distiled water for everything.
There are some people that get enjoyment from taking total control of the process and their reward is being able to take a photo, process it, and print it and know exactly how it will turn out. There are also professionals that need to have a print turn out the same every time. I'm neither of those, but if you are, use stop bath.
Even the worst photo processing places treat their water before using it, there is a reason for that.