In Europe, the most popular high school and university debate format is British Parliamentary in which spreading is not popular because you only have 15 minutes to prepare and weakly justified arguments don't require responses.

https://youtu.be/XyIK_Cg_8jc?t=327

British culture certainly has plenty of ivory tower elitism, yet has passed by this. I don't think it's a special revolutionary pedagogy, just a different interpretation of how to deal with subjectivity in debate.

To play devil's advocate people seem to be quite attracted to self-sabotaging ideologies, as they offer the intoxicating justifications of "not my fault" and "no point in doing work". Hell, the typical "rebellious" things are practically hand-picked to be ineffectual at gaining any even small sort of power and demonize doing so. Just look at the dynamics of being accused of "selling out".

I agree with you that it's incredibly bizarre, but I associate it with the strange cultural norms that can only crop up in very specific academic environments that have just the right alchemy of academic strangeness, competitiveness, and idiosyncratic historical origin. I'll compare it to something I recently discovered, which is some viral video I recently saw of some sort of pig fare where kids lead pigs out on this walk to show how well the pigs are trained and I think to show off the pigs as models specimens, and the kids do this intentional intense eye contact with judges in order to get the judges to look at them. It seems so strange and abnormal, but it was explained away as just something that's part of the history of the competition and having strategic value for being effective in the competition.

I've seen videos of the college debates you're speaking of though, and I've definitely felt that they're badly in need of reforms that either impose a word count or otherwise disincentivize speed reading.

The long and short of that is just to say you can explain it without regarding it as some sort of intentional state disinformation program. I would also say I find that especially implausible just because, while I don't love the practice, I don't think it degrades our ability to follow arguments or have information literacy necessarily, and meanwhile modern social media absolutely does seem to instill habits that reinforce short-term attention spans, disjointed thinking, object permanence problems and the like, all of which would dispose people to be more receptive to bite-size arguments that don't have to fit into a comprehensive or coherent worldview.