Like the title says, I couldn’t see it happening in the source code, only if the entity has 0 components attached to it.
It does remove all components and delete the entity. The only exception is SystemStateComponents(https://ecsy.io/docs/#/manual/Architecture?id=system-state-components). If any of those are on your entity its the job of your system to remove them after all regular components have been removed. After the last SystemStateComponent is removed the entity is automatically removed completely.
How this works is also demonstrated in this demo: https://ecsy.io/examples/#System%20State%20Components