One more follow-up:
I did, in fact, receive my "failed" (but designated 'good' by ProParts w/their torque value of 160 ft#) component but I had already installed the replacement one from MSP.
(I'm now the proud owner of 3 of these hubs! Yay!)
As I had already started the process of the swapping, I returned the original MSP RF hub to its location, torqued to 160 and sealed it up.
Installed the replacement MSP LF hub and torqued to 160 and sealed it up.
Went to the Glen and ran the test day and a single race group.
Only issue identified was on the LF which I (ultimately) misidentified as hub play.
Another R&R of the LF hub shifted my suspicions to the lower ball joint.
Then upon arrival of a more experienced mechanic he identified what was presumed to be inner tie rod play.
Anyway....Everything reinstalled back on the spindle!!
No further issues that weekend apart from some bone-headed driving by yours truly....
Where does that leave us?
I personally have now ran two different hubs at the LF corner on tracks with serious, long length & high speed right-hand turns; one exhibited noise near the end of the weekend (while 'under torqued' per MSP/ProParts) and the other, while used less than the first, has presented zero issues while torqued at the MSP/PP specified value. Also I still have a previously noisy hub to disassemble and report back on anything discovered.
As I noted before, I may be merely reaching a point of performance/speed that could accelerate wear issues going forward. But whether that means I should be changing my maintenance procedures (from annually swapping hubs to monthly for example) or deciding on a level of disposability for them is still uncertain. "Right now" I've never experienced a "wheel separation event" (regardless of where or on which axle it happens) and I hope to mitigate that likelihood by being more meticulous about checking my hubs between sessions.
I leave the debate on what the Mazda engineers were trying to accomplish with the hub design to the machinists and metallurgists on the board...but if someone comes up with a viable replacement that we can get SCCA/NASA to sign-off on all the better for us!