Supplemental madness: on the hunt for 'Figure S1'

I've just been looking at this new paper by Vanesste et al.  in Genome Research:

Analysis of 41 plant genomes supports a wave of successful genome duplications in association with the Cretaceous–Paleogene boundary

I was curious as to where their 41 plant genomes came from, so I jumped to the Methods section to see: 

No surprise there, this is exactly the sort of thing you expect to find in the supplementary material of a paper. So I followed the link to the supplementary material only to see this:

So the 'Supplemental Material' contains 'Supplemental Information' and the — recursively named — 'Supplemental Material'. So where do you think Supplemental Table S1 is? Well it turns out that this table is in the Supplemental Material PDF. But when looking at both of these files, I noticed something odd. Here is Figure S1 from the Supplemental Information:

And here is part of another Figure S1 from the Supplemental Material file:

You will notice that the former figure S1 (in the Supplemental Information) is actually called a Supporting Figure. I guess this helps distinguish it from the completely-different-and-in-no-way-to-be-confused Supplementary Figure S1.

This would possibly make some sort of sense if the main body of the paper distinguished between the two different types of Figure S1. Except the paper mentions 'Supplemental Figure S1' twice (not even 'Supplementary Figure S1) and doesn't mention Supporting Figure S1 at all (or any supporting figures for that matter)!

What does all of this mean? It means that Supplementary Material is a bit like the glove compartment in your car: a great place to stick all sorts of stuff that will possibly never be seen again. Maybe we need better reviewer guidelines to stop this sort of confusion happening?