Google up "rotor phasing", there are some MSD videos. The whole deal is, the magnetic pickup produces both a positive going and negative going spike (or the other way around) as the reluctor rotates past the pickup. The "box" whatever you are using ONLY TRIGGERS on one of them. So if you reverse the wires, now the two spikes are MOVED IN TIME or distributor degrees of rotation in relation to some arbitrary fixed point. This moves where the spark triggers in relation to the cap tower contacts, and not only moves engine timing but causes cross-firing in the cap
I've never run Mallory but surprised they don't document this better. Another example is the Mopar dist triggering a Mopar ECU, a GM HEI, or "some other" box like the Hyfire. Anything magnetic, you reverse the leads, phasing/ timing will be badly affected
