scrollbars and any arrow buttons they offer arent HTML elements, these scroll affordances are very similar to those, just easier to style and customize.
v2 of the spec will allow you to "bring your own buttons and links" that the browser will wire up as if they're scroll buttons and markers. but to keep the accessibility easy (aka less foot guns) having the browser manage them has a lot of userland benefits.
and yep, we're working on JS events and integrations more in v2 also!