Yes, I did. That's what I meant when I said "pre-fogged." Perhaps not the best choice of words by me. Probably should have said "threshold fogged."
A test was first made to determine threshold exposure for the Bromide #3 paper. Then the test sheet was pre-exposed to just below that threshold level. Any additional safelight fogging exposure should have therefore been immediately visible after development. Either to my eye, or to the far more sensitive reflection densitometer. Comparisons were made against a similarly pre-exposed control sheet that was not subjected to the safelight.
It should also be noted that 30 minutes was an arbitrary cutoff by me. Because there was no detectable fogging, the actual safe time limit was therefore an unknown time beyond 30 minutes.
When I later performed similar testing for a DIY red LED safelight under Rubylith, I extended the test out to 60 minutes without any apparent fogging on MGIV. That's where my earlier incorrect reference to MGIV came from.