Clock management is a pretty big aspect of (American) football strategy and very much expected. I don't think anyone considers it gaming the rules. Just off the top of my head:
- Teams with comfortable leads tend to switch to conservative play calling. This keeps the ball safe and the clock running.
- Inside of 2:00, getting tackled on the field keeps the clock running. But running out of bounds or throwing an incomplete pass will stop the clock. So plays are always chosen to take advantage of this.
- Quarterbacks will spike the ball to quickly the stop the clock (incomplete pass).
- Calling a timeout stops the clock, so teams save these for the 2:00 drill. The 2:00 warning also stops the clocks, teams consider this a free timeout.
- Coaches will call timeout just as a kicker is about to kick a field goal. This is called "freezing the kicker". When timed right, it makes the kicker have to kick it again.