If your placement of the cue ball is slightly backward from where they're breaking from, that will give you the increased speed you're seeing in the app. It took me a long time to try and figure out what dials in the most perfect results for the breakspeed app. Placement of the phone in relation to their breaking position is what matters the most, solely so the phones mic gets a clean capture of the break. I've had three phones on different spots of the table all give different results. They were all within 1mph of each other, but the same app on the same break gives different results. Now the variances of cue ball placement allowed for more than a 2 mph difference.
Also, don't be influenced by how high the ball jumps up on the break as an indication of how hard it was struck. How far backwards the cue ball rebounds is a better indicator. When SVB breaks and the cue ball rebounds back to the first diamond before the side pocket and second bounce stops around the kitchen line, that's a 27 mph break. Having the cue ball rebound to the side pocket then stop at the diamond between the side pockets and kitchen is around a 25 mph break.
But you're right, now that SVB is using the extension, he is using his break cue more often.