A simple but sad explanation would be that it is dependent on the reviewer, or more likely reviewers, over at Apple. E.g. if Sandeep finishes reviewing faster

A simple but sad explanation would be that it is dependent on the reviewer, or more likely reviewers, over at Apple. E.g. if Sandeep finishes reviewing faster than Nikolai, then those lectures will go up faster. The Apple "new improved textbooks and courses" thing suffers from the same problem, I had a look at one (on geometry and trig) and things were out of sequence.