The R1 has a lot of memory bandwidth. According to this article at Tom's Hardware[0], the M2 has 68 GB/s of memory bandwidth. So the R1 has several times that at 256GB/s. Coincidentally (or not), that is similar to the discrete Nvidia and AMD GPUs they compare the M2 against in that article.
I know discrete GPU comparable memory bandwidth doesn't necessarily mean it's discrete GPU or a peer to the M2, but there's clearly a lot of something going on. Plus isn't it kinda weird to specifically mention a spec that is applicable to programmable devices like CPUs or GPUs on a signal processor? Like, who cares?