Correct, you'll need to get a " Certified Position Source" or TSOd GPS receiver to use with the KT74. They don't tell you the details of that upfront. I think they should offer a KT74 + GPS "bundle" if they are going to call it 2020 compliant. This would avoid confusion.
The iFly is WAAS, but it is not Certified, actually no portable device can be. I hope this clears any confusion.