Even if the wave isn't very tall, if it is fast-moving it can knock you off balance. Once you're down, wave doesn't have to be very tall to drown you. There's also the fact that rip currents are commonplace phenomena on beaches all over the world, so you combine that with a single unexpectedly fast wave and it's easy to believe a few people would die.
but, is a rip current a natural disaster? Natural, sure, but to me it's a regular phenomenon, similar to a small tsunami
According to the "quick bulletin" on the bottom, this seems to be a downstream effect of a magnitude 6.9 earthquake that occurred. I suppose that will generally be the case for a tsunami, something usually drives it. In this case, it appears they're assigning 0 deaths (or stats) to the tsunami, but 2 deaths for the "total effects."