From what I understand Sander, it seems the issue is not in the Waves menu itself, it is the Sonar menu above it (in the same window) where you can select presets, in the grey title bar area.
Quite a common issue it seems, I have a number of plugins that will and will not work in this area of the UI (NI for instance). Some plugins will show the presets but don't get the titles of the presets correctly, or some plugins just won't show the presets at all.
I am assuming then these particular plugins are not exposing their parameters to cakewalks plugin engine correctly to be consumed, or there is a bug whereby Sonar is not parsing the information consumed correctly into the menu. The only people who will know what the issue is for sure is the developers as they have access to the source code (although it should be noted many plugins work fine in this area), as Cake does not have access to third party plugin code the third parties are basically the guys who need to check exactly what is going on here (and contact Cake if necessary, if they find no bug in what they are exposing to Sonar).
Either way there is a workaround.
There also seems to be an issue with presets persisting.
I'm not sure Waves plugins had updates or not since X3C.
We also had a confirmation from Cake that:
"BTW with Waves there is a bug in their VST3 preset implementation currently where changing a preset in their UI doesn't update SONAR. I will be reporting that to them."