I am unsure if that is completely true as my past experience in the lifestyle was that everyone was very on top of regular STI (think you meant this not SDI) testing and safe sex practices to protect all involved, whereas normal dating there is a lot less of that plus secret polycules you are not even aware you are in (cheating). Not seen a study on this but this was my observation at least.
STI you are correct. I realized this earlier when I was reading reading. I will fix.