Is it common?....Yes
Is it required?.....No
It's just an after-effect of delivering the stroke. You will always be shooting a break shot (and most shots) with the back end of the cue slightly elevated higher than the front end. This is because of the rail. The rail height is near the center height of the cue ball, and you cannot deliver your cue perfectly level while swinging your cue over the rail. Maybe you can if using top english, but I don't recommend using top for the break.
If you see the pro "power break" in slow motion, you will see the cue tip aimed/contact the center of the cue ball, or slight below center when they want the cue ball to draw back a little. You will also see the cue ball is actually off the table. It's like a jump shot. The cue ball is flying to the rack, literally.
Not all pros power break. Neils Feijen set an example with a soft break that would pocket the head ball in the side pocket on more than 50% of his breaks. A lot of players caught on, and so did the tournament directors. You'll find a lot of tournaments will not allow soft breaking.
Don't worry about what happens after the cue tip contacts the cue ball.
Concentrate on delivering the cue tip where you are aiming at on the cue ball.
