Good catch JarryG. I think what u say is correct. Interestingly, patching to ESXi 5.1.0 Build 914609 seems to result in no "unknown" statuses in Configuration, Health Status - this applies to the DQ77KB lab and also a Shuttle S77 based Lab.
I'll patch an Intel Hanlon Creek (S5520HC) Server (has integrated BMC) running ESXi 5.1 to the latest and see if this fixes Health Status issues - there are a few people who have complained about this.....and it looks as though the issue may be resolved.
JarryG what ESXi 5.x version and build # are u running?