There is indeed a difference between scheduled publishing in CM and in Experience Space.
CM allows to schedule either beginning of publishing or beginning of deployment.
In Experience Space we currently only have the option for scheduled deployment. So the rendering is done immediately. The more publishing is delayed, the more chances that we will publish other versions of content than what it was at the moment of scheduling. In other words, you cannot be sure that the proper content will be published.
Is there a particular use case why you would need to schedule publishing instead of deployment?