Thanks for the links. Just noticed this statement on the MKS product pages for EZY pedals:

"​​​​​​A thin pedal spanner (15 mm wrench flat with under 3.2 mm thickness) is required for initial attachment of the adapter.
For the installation of Ezy Superior, we recommend you to use dedicated MKS original PEDAL SPANNER or thin wheel hub spanner."

Again, I can't post a link, but that statement is near the bottom of MKS pages about EZY pedals. It seems MKS is okay with using cone wrenches to install their pedals.