For the record, transients can be extremely strong with P.A.F. style HB's. If the test mentions peak voltages (and I think it's the case like in the measurements done here), I see how it could give such results : my experimental data rate a Burstbucker Pro @ 660mV while this pickup was not
that stronger than other P.A.F. clones when played... A good part of the output level was in the
attack with this A5 unbucker.
Also and FWIW: in my archived data, a
same P.A.F. clone in neck position delivers 150mV more than in bridge position - reason why there's "neck" and "bridge" models, basically.

) So, the SH-1n in the test above should spit 422mV once in the bridge slot: it "sounds" possible to me... but YMMV.