Saw a minor league game a couple weeks ago. Pitch clock was 15 seconds to throw a pitch if the previous pitch was a called outcome and 20 seconds if the ball was fouled off. It reset to 15 seconds after a ball in play and started as soon as the pitcher got the ball and was back on the mound. There weren't a lot of throws to first, but such action did reset the clock to 15 seconds.
The first 5 innings were completed in slightly over 1 hour. The last 4 took about 1 1/2 hours due to pitching changes and increased scoring. Still, a 2 1/2 hour game. Now, the fact that it was in the 40s may have contributed.