They are harder to zip up later in the day. Your legs have less water retention first thing in the morning. You can wear them for a whole day walking around or completely soak them in warm water, inside and out, with your leg IN them, and wear them until they dry. A good gauge of time be try Saturday or Sunday morning, soak, wear to barn and ride, wear home.
the water method is to encourage stretching, not shrinking to fit your leg. They will stretch where the most pressure is, in this case, around your calf. It won’t hurt them. Personally, if the boots are so cheap that getting them wet will debilitate the glue used, they won’t be lasting long anyway. Most boots don’t rely on glue to hold them together.