At the beginning of the life cycle of a project or a sub-project, it is absolutely normal to plan a meeting without necessarily that the end date has been determined for this project.
For example, in fact, it makes sense to have a scoping meeting or brainstorming to determine the key dates and project milestones: number of delivery, documentation, installation, testing,
end date, the duration of the observation of the stability, etc.
It is very odd that the management function of the date of a meeting "imposes" itself, the end date of the project !
This is , in my opinion , an exception to implement around this feature of management/planning of meetings.
As long as the end date of a project is not registered or approved by the Project Manager, a meeting must remain a " meeting."
A meeting should not be able to force the end date of the project
without even display a warning popup to the project manager 
!!!
Because the risks and the consequences are simply very important.
The end date of a project is not a trivial event

!
So this is extremely inconvenient for any Project Manager.
In summary, it would be useful , at least:
- To add a function that displays an alert pop-pup to the Project Manager or triggers a validation workflow before going further

.
- Allow to the user the choice to distinguish the meeting date and the end date of the project.
Sincerely,