Different products are made to cover multiple use cases. The WCOs are good for those use cases that want to use either the PIR detection system, have no way to get constant power to a location, want a more portable camera, etc. The V3, V3P etc are outdoor rated, but made for those use cases that need continuous recording, have power at a location readily available, etc.
The Solar panel is to assist the WCOs at their locations where power isn’t available. The WCO has its “sleep mode” where the small amount of power the solar panel can supply can charge the WCO fairly well, dependent of your event frequency of course and live view usage.
There is this existing wishlist topic:
to help the cameras that need the constant power. Give it a vote if you want to help it along!