It's been a while since any new eruptive fissures opened, despite all of the rift's threatening to move west. The eastern vents have closed, which you wouldn't expect if there was some extreme overpressure. Looks - at least as it stands - like the current vents are dealing with the flow rate.
Fissures are not unusual when it comes to basaltic volcanism, and you don't have to have the main crater erupting at the same time, by any stretch. More often than not, the magma will even basically "erupt into the ground" - splitting a dike but with the magma never reaching the surface - to those on the surface, it comes across as nothing more than a propagating quake swarm. An eruptive fissure is a surface expression of a dike.
Oscar would be more familiar with the ratio of fissure to crater eruptions in Hawaii and their typical behavior, but where I am, most eruptions are fissure eruptions***. It's usually the thicker, more explosive andesitic / rhyolitic lavas (e.g. characteristic of volcanoes in the Ring of Fire) that are reluctant to stray far from their main crater.
*** One big difference is that we're a spreading centre while Hawaii isn't. So for example, we don't get "3 decade-long very low flow rate eruptions" like they do; we tend more toward massive lava eruptions, 3 months to a couple years long.