> and with zero justifications for why this would suddenly add a "large cognitive load" to Wikipedia
Because if a video about say, 9-11 conspiracy theories, will have an infobox added to it which quotes the first par of a Wikipedia article, makers and viewers of such a video will go to Wikipedia and edit the first par to front-load the information they want to see. This will happen extensively across hundreds of thousands of topics. Many of Wikipedia's policies and processes won't apply to these new edit wars because they are about whether or not information can be included, rather than which information appears in the introductory part.
Because if a video about say, 9-11 conspiracy theories, will have an infobox added to it which quotes the first par of a Wikipedia article, makers and viewers of such a video will go to Wikipedia and edit the first par to front-load the information they want to see. This will happen extensively across hundreds of thousands of topics. Many of Wikipedia's policies and processes won't apply to these new edit wars because they are about whether or not information can be included, rather than which information appears in the introductory part.