Videos are not documentation.
They can be used to demonstrate examples of how to do a particular task, but as other commenters have mentioned, documentation involves listing classes, functions, parameters, etc and clearly explaining what they all do, in a searchable manner. Text is searchable, video is not.
It would be very beneficial to have clients that support aggregating equivalent communities from multiple instances. When viewing a post from the aggregated community there could be a section at the top saying “Viewing comments from:” and then a dropdown to choose between “all instances”, “lemmy.world”, “lemmy.ml”, etc. When viewing all comments, they would be in one combined feed, without the user needing to care about which underlying post holds the specific thread they’re looking at.
Similarly, when users post something to an aggregate community, they could select whether it’s posted to all the included communities, only one, or some specific subset.