Nokishita has updated their information and included information on the mount. It does indeed appear that the RF mount is a shorter registration than the EF mount, and it requires an adapter to use EF lenses.
That is sure to please some that want to adapt lenses to the RF mount, and will disappoint others that were hoping for native EF compatibility as we surmised before.
M adapter R was confirmed with “Mount Adapter EF – EOS R”. Three types of mount adapters are available with control ring and drop-in filter.
The ability to use drop-in filters will certainly make this more than just your regular “dumb” adapter and add useful benefit to using EF lenses on an RF mount.