The study does not support such a conclusion.
First of all, 87% of the 1800 valid responses reported using commercial binders vs 16% for elastic bandages, so you would expect that with a bigger number of women using these binders, you'd get more adverse reactions, especially if they don't happen as often.
Second, the authors surmise that commercial binders may be associated with more negative outcomes because they are misused (that is respondents may be buying them in a much smaller size than they should). So from this study we do not know whether commercial binders - if sized correctly - may be less damaging.
Third, although binders may be associated with more negative outcomes than elastic bandages, this doesn't tell you much about the nature or severity of the issues. When it comes to rib fractures for instance, commercial binders were not associated with rib fractures whereas elastic bandages were the biggest risk factor for such an outcome.
Essentially no method is safe, so the authors recommend the following:
Healthcare providers may be able to help their patients reduce negative outcomes associated with binding by recommending ‘off-days’ from binding when possible, avoiding elastic bandages, duct tape and plastic wrap as methods for binding and using caution with commercial binders.
In other words, they come to the conclusion that not binding at all on at least some days would be most beneficial.
And here's the recommendation that Mermaids should pay attention to the most:
In addition to frequency, duration (number of years spent binding regardless of frequency or intensity) was independently and positively associated with 13 health outcomes, particularly skin and soft tissue outcomes and musculoskeletal outcomes. Reducing duration by delaying the onset of binding, if possible, may reduce the risk of experiencing the negative physical outcomes explored in this study.
This study only looked at adult women. Although some will have reported binding as minors (duration for almost all was at least 1 year of binding, longest was 4 years) and they collected responses from those aged 18 and over, with 18 to 24 being the biggest age group, none in this study were binding from as young an age as the child Mermaids offered a binder to. I'm also not aware of any other study looking into the negative health outcomes of binding in minors at all. This makes a big difference, because the adolescent body is uniquely vulnerable in a way that an adult body is not. And the younger the child the less likely they are to (be able to) follow the instructions.
As our bodies still develop further in young adulthood, it makes perfect sense that the authors recommend delaying the onset of binding for as long as possible, because damage is more likely in an immature body. It's not rocket science, is it? And obviously, the later binding starts, the less the duration overall.