Are you sure it stops the clock?
Here is what I could find on the web (it is from the Puerto Rico event last year):
Shot Clock
Tournament Management may implement a shot clock in any match at any point of time at its discretion. The time control for the shot
clock is as follows: 30 seconds per shot, one extension of 30 seconds per rack, extra 30 seconds for the first shot after the break. The
“time” signal will be announced by the referee or sound automatically when 10 seconds are left. By default, time will not be paused for
any assistance with bridge or cue ball cleaning. The referee may decide to stop or reset time; in which case they will announce the
amount of time left when the time resumes