The man page has been updated to reflect this change. When it fails you know it pretty quickly and failure will cost you some lost work. 1 Linux offers the possibility of interleaved swapping across multiple devices, a feature that can gain you much. However, software raiding swap across multiple devices adds more overheads than you gain. Remember that the fstab file is very sensitive to the formatting used, read the man page carefully and do not just cut and paste the lines above.
Some people use a RAM disk for swapping or some other file systems.
However, unless you have some very unusual requirements or setups you are unlikely to gain much from this as this cuts into the memory available for caching and buffering. Speed Very high. Keep an eye on these directories, not only for hidden files but also for old files. Also be prepared that these partitions might be the first reason you might have to resize your partitions. Often programs will warn or fail gracefully when these areas fail or are filled up.