To add to notes for the original post on different behavior between BIOS 03.94 and 03.96 with the Z420, I tried the latest version once more with another CMOS reset to see what would happen out of curiosity and ensured that Fan Idle Speed was set to the lowest value to observe fan behavior.
In addition to the Tjmax value having been adjusted from 90*C to 95*C for the Xeon 1650 v2 in 03.96, the CPU fan now waits until the reading hits 85*C before ramping up to cool the processor off instead of the previous value of 80*C. Interestingly enough the reading in HP Performance Advisor now also matches what other software reports for the CPU Package temperature instead of being approximately 5*C higher which was the behavior in 03.94 and below.
Something else to note is that pushing the CPU with a stress test such as MSI Kombustor's CPU burner or Prime95 will only cause the clock speeds and voltage to throttle slightly after hitting the 85*C mark (4290 MHz to 4080 MHz from my brief testing), whereas previously mentioned 03.94 will throttle once it hits 80*C and pushes clock speeds much further down to 3790 MHz (with a 43x multiplier set, with this CPU at stock clocks this drops to 3490 Mhz).
Overall for overclocking, at this time 03.94 appears to be the best choice for stability and my system is currently rock solid with that revision with a 43x multiplier overclock using the methods I posted earlier. However this situation is a bit conflicting, as 03.96 should in theory allow the system to perform better with higher clock speeds under load with less throttling involved as observed, but the system is less stable under 03.96 than 03.94 with the same values likely due to a brief peak to Tjmax which causes the system to power down and back on in order to protect the processor from heat damage. I'll test this theory again once I have the larger heatsink from the Z440 installed to see if the shutdowns are indeed caused by the thermals or if it might be something else.