It is only true if Player or Character are destroyed, which is not the case if they only respawn or disconnect.
Many developers actually expect them to hang around after those events.
On the server, you can opt in to an option for Character/Player destruction: New Player and Character Destroy Behavior
We did get some requests to enable this on Client as well, but that’s currently not available: PlayerCharacterDestroyBehavior doesn't function on the Client
While testing that feature, we found a good percent of games on the platform will become broken, so it’s unlikely that automatic destroy for Players or Characters will become possible in the future (See update in New Player and Character Destroy Behavior Enabled by Default)