Yes it is true.
Explanation - If your hard drive can read/write data at 1.5gb/s that means your computer can you a certain amount of memory at 1.5gb/s.
DDR 3 - 800 has a transfer rate of 6400mb/s. If you transfer data from the cpu through the fsb at the same rate then to the hard drive now the data has to sit in a buffer while it is being written at 1.5gb/s while the driving is still trying to access other files you are working on. You have to share the 1.5gb/s with the page file and all other activities you are doing on the computer.
If you store the page file on another harddrive, you will have the OS drive using 1.5g/s read/write for activities while the second drive speed(1.5g/s) is dedicated to just read/write of temporary memory. This would decrease the bottleneck and reduce the amount you have to store in a buffer while the drive is reading and writing. Still considerably slow compared to the 6400mb/s of memory