This "buffer period" is a very usefull idea.
But it would be great if it an additional option could be set: to apply only on existing booking.
For example, Dave (personal trainer) is avaiable from 9am to 6pm.
But for outside coaching, he would need additional time to be locked on a purchased appointment, 30 min to onsite, and 30min to come bakc to the club.
At this time, with the buffer option, he would be avaiable only every 2 hours (if min block bookable 1 hour)