Not really, it shows that MS have optimized things to make their own app as fast as possible. A 50Mb doc loaded from an SSD will be faster though and using any other app that doesn't pre-load itself will also be faster with an SSD.
Hard drives have no problem with continuous streaming of data like loading a movie - that is a great use-case for them. But for the type of access that happens with an internet cache, the mechanical nature and latency of a HDD makes them much slower than SSD.
Again, you're correct with all of that. A user who is routinely opening 50mb files, users like you and me will notice a benefit. Users like Kate, where she'll spend most of her time on here, youtube or one one of her many man-porn sites won't notice the difference.
The point I'm trying to get across isn't that SSD's aren't better than normal HDDs, they obviously are, in lots of scenarios, but for a lot of home users, due to the way they use their laptop, the benefit of larger storage will be greater than the slim increase in speed that they'll see with an SSD.