I do think it comes from a lot of presumptions on our part, though not entirely baseless: it's a combination of him being known foremost as a jump specialist, his (recent) skaters not being particularly known for their ss (as well as Nathan not having made as much improvement in ss as many would've liked/expected since his junior days when he was known particularly for his skilled blade work and for being a very well rounded skater), and Nathan's own devotion to quads in the recent years (which I get the feeling Raf is not 100% supportive of).
I think the verdict is still out though and I'm reserving judgement. I've cited Alexander Abt, his pupil of the longest time span, as an example of impressive skating skills as well as nice lines.