You misunderstand how that's supposed to work. You don't "free main memory" to SSD. The idea is to use SSD as a pre-buffer for RAM, so it's quicker to access than reading from disk.
But there's something wrong if the Linux kernel buffers SSD I/O in main memory and swaps code fragments to disk. At least that's what happened in my experiments.
I've been toying around with a Samsung 16GB SSD. Performance improvement over spinning disks in an I/O-heavy scenario was neglegible. Also, it seemed as if the Linux kernel was still using memory to buffer SSD disk I/O. Which somewhat negates the argument of using SSDs to free main memory for other stuff.
Any idea what type of OS/filesystem combination they were using?
I really hope they publish the stuff as Linked Data.
The only possible interpretation of any research whatever in the `social sciences' is: some do, some don't. -- Ernest Rutherford