Not true. I have gone off coffee and caffeine a couple of times over the last 6 or 7 years. When I drink a few cups of coffee, I'm up to the bathroom a half dozen times a day. When I switch to a water bottle, I only have to go maybe once per day (during work hours). The difference is stark and the amount of liquid is not the issue.
Is immature snarkiness really needed when someone is talking about a real physical effect carefully observed over years?
Caffeine gives me an urgency to urinate. Having that first urination in the morning after drinking coffee is just like the effect many people describe after drinking the beer. See "Breaking the seal".