Not true at all.
My E8600 could pass several passes (5-10) of IntelBurnTest but failed Orthos Small FFT.
I had to raise vcore from 1.34 to 1.36 for Prime small fft stability on my E8600.
Funny enough, my E8400 was the opposite. Primed all day and night no problem, but wouldn't pass IBT (this was at 4.2GHz 1.36v)