I hope that's intended as a sarcastic comment because the statement on its face isn't true.
This study strictly looks at functionality and concludes that the FFSMs should be as functional as a traditional snorkel. What we don't know is fatality rate for each. In other words, in the universe of snorkelers, how many die per year vs in the universe of FFSM users, how many die per year. If the rates are the same, then there's no difference between the two.
My suspicion - absolutely NOT supported by any data - is that the rate for FFSMs is higher. And I think what you need to factor in, and I posed this as a written question at the end, is why people are using a FFSM. usually it seems it's because they don't want water on their face and they don't want to get water in the snorkel.
If that is correct, then the finding of the study that the masks are somewhat prone to water intrusion becomes significant. Because if you get these to avoid the water issues and you get them, does that change your rate of breathing (anxiety/panic) which then brings into play the finding of a greater work of breathing with some of the FFSMs, and the two of those together ma prove to be a fatal combo.