It seems that one of (or both of) a couple of things may have been the root cause:
1) Timing of initiating pre-landing checklist (from which the FO tests A/SKID and ensures ARMED). Initiate "just after" lowering gear, let's say @ 10nm from RW on APCH).
2) I may have been pushing the toe brakes unknowingly on my rudders during final approach ... could that cause an alert of this nature?
After watching the final approach component of the "marathon flight" from January, I have fine tuned my process. Flaps 20 transitioning from 200 kt to 180 kt; flaps 30 @ 180 kt transitioning to 160 kt on final, drop gear and then initiate before-landing checklist as intercepting GS or around outer marker. This process resulted in no A/SKID warning on final approach.