Simon-
Check
this post for some comments on this topic.
The answer to your question is that the only way to know for sure is to inspect the exact machine that you would be buying. Harbor Freight has been known to carry both higher-quality Rong Fu equipment and cheesy knock-off clones, and sell them through the same catalog number. Since a typical price for a new Rong-Fu RF-31 is in the $1500-$2000 range (based on the options included), I would be very surprised if that is what is being offered. I would suspect that this Harbor Freight machine is yet another RF-30/RF-31 clone. As such, I would be very cautious about the condition and quality of the machine until I had inspected it and determined if it was suitable.
Also, I would take this as a big clue: if a company does not care enough about their business to even proofread their catalog copy to ensure that it is correct and error-free, then how likely are they to care about me as a customer? (i.e. read the catalog page you referenced very carefully - does the quality of their product description give you confidence in the quality of their merchandise?)
-dave