Not OP, but it is possible for something to be both "obscene" and "helpful" (maybe we should say "of value"?) Say... footage of Hiroshima? Or the liberation of concentration camps? I'd say those are examples of things that are both obscene and have value.

So I think you're looking for another property those videos have in common. It might be closely related to obscenity, but I think it must be a bit more nuanced than that. Why are those videos valueless? (I don't know the answer).

Depends on how you define helpful or how much of a requirement for content to actually be “helpful”.

A strict definition might require content to have academic or intellectual value (implied by the remark about it being shown in an academic context) but this would also exclude a vast majority of non “obscene” content. Further, if you could swap the obscene elements for non obscene elements, I would argue the “value” of the content, as measured by its helpfulness, stays the same.

This all moot, however, as it’s likely not the right conversation to have. There is more useful discussion to be had on harm caused as a result rather than any sort of value judgement.