Their earlier material had a more metallic sound and also growled vocals featured rather prominently in places, but they were certainly always on the fringe.
As Don Corleone somewhat mentioned, they later morphed into Kayo Dot, which has slowly stripped the metallic aspects away (their last release, Blue Lambency Downward, being some kind of avant garde-chamber-jazz music or something).
It doesn't surprise me that this new maudlin album is much more mellow, as Toby Driver explains in the booklet of the Leaving Your Body Map reissue that 'Interlude IV' from said album was basically the epitome of what maudlin were working towards, and Part The Second is far more in line with that type of thinking.
So Slunk, I guess now they are really just metal-by-association, much in the same way that a band like Anathema or Katatonia are now.