Well a senior developer would be assumed to share a certain common understanding of concepts and terms that a more junior developer might not. When teaching anything one of the most important parts is ta gauge your pupils and determine whether they need more or less information to keep the topic interesting while not making it impossible to follow along. Since written or otherwise pre-recorded teaching materials aren't afforded the luxury of interacting with their pupils they must choose ahead of time what level they are aimed at. And since a senior in any field would be able to follow along with materials meant for the junior, albeit at a slower and less interesting pace, but not the other way around they tend to err on the side of over-explanation. A platform for teaching senior developers would therefore allow a more engaging and time saving experience for those able to consume it.