The Appendix 1 in the report has case studies for three of them. There are loads of companies that operate this way, but they've just highlighted the ones that most often came up in their study. Certainly the first one, when I looked at their website a few years ago, said they operated a hybrid model and I understood what that meant and steered clear. See here: https://societyofauthors.org/SOA/MediaLibrary/SOAWebsite/Documents-for-download/_REPORT-Is-it-a-steal.pdf