I must admit that I have never conducted a DSD in a resort situation. I've done them in pools and off LOBs a fair bit though. So what makes resort situations unique and pertinent to this discussion?
Many resorts (Sandals type all inclusive) offer the resort course as a free benefit, part of the all inclusive package, so the staff does a ton of these a day. Many folks who cater to the cruise ship market also do a ton of these a day. The ratio is now 4:1, it was 8:1 the year I did 8 or 16 a day, 313 days a year.
This instructor might as well have been in a resort. We called it churning and burning. What we don't know is how many bolters he's ever had, how many times he's lost control of his student, how many times things went wrong according to standards and everything was all right. All of the folks who talk about "just reach out and grab him when he bolts" have never made their living doing this. You might have to go through another student to get at the one who is having a panic, causing another panic. You think 4 students all dive close enough to the instructor that he can look in their eyes the whole time and assess the impending bolt? In this instructors case, he had to evaluate 3 students at the same time, the whole time, and how does anyone prevent a bolter anyway?
It's great doing 1:1 DSDs, it's how I took my Step Mom and Dad resort diving in Belize the year I got married. That isn't the reality of resort diving. In resort diving, the van dumps off 12 strangers from the cruise ship. You have 6 hours to get them fitted in gear, 2 hours in the classroom (that you learn to do in an hour and 15 minutes), 1 1/2 hours in the pool, fill their tanks while they eat lunch, load their gear on the boat, take them to a boat ride and for a dive, and get them back to the cruise ship by 3:30. 6 days a week.
Those who would puff their chest out and say that the instructor should be close enough to prevent a bolter at all times don't understand the reality of resort courses.