Yes, I know that the 1730i has only one controller/CPU (as the vendor calls it). The problem is interpreting that footnote in the VMWare compatibility list as referring to that trivial fact and not to some limitation in how storage path failover can be done between VMkernel and the 1730i.
I have now compared the compatibility list entry with the one for the dual controller variant of essentially the same hardware (1830i) and it omits the footnote while also stating that the 1830i is somehow ESXi 5.1 compatible but the 1730i is not.
So I guess you are right and someone chose a really bad way to state that "this model has no redundant storage processor". In a context that might talk about Storage Path failover or more rarely Storage Processor failover, abbreviating the rarest phrase to "SP" is just not readable.