As I recall (multiple) sources claim the PTs did attack the BBs - they may have "kettled" them - but failed to score any hits and then it fell to the DDs - likewise, launching every torpedo they had - to actually hit Yamashiro and Fuso, the latter breaking in half right then and there.
But you're saying it was the PT torpedoes that scored that decisive blow - and so we have (yet) another discrepancy between the conventional "wisdom" and some other interpretation(s) of the record?!! This would be BIG - another one to rival even the "Hood-Sunk-by-Prince Eugen-as-opposed-to-Bismarck" debate!
Now I do know that even the respective roles of Yamashiro and Fuso - which one broke in half, and which continued on, into the radar-controlled USN BBs' gunfire - has (at least once) been questioned. By none other (at least) than the author of "Anatomy of The Ship HIMJS Fuso" who, IIRC, believed it was Yamashiro that succumbed to the torpedo attack, and Fuso that went on to face the USN BBs.
However, this question - whose torpedoes achieved the initial, devastating ambush - is much more crucial, and potentially interesting, IMHO. And, though in the end I never was convinced of the argument for Prinz Eugen - and granted the evidence is so scarce and fragmentary it seems far from conclusive for Hood, either - still I would be VERY interested to hear who/where did you see any indication(s) that the Surigao PTs were the ones whose torpedoes really struck home. So, talk to me, Donny!
Also - a point of interest: PT boat torpedoes were visibly (very) much shorter than DD torpedoes - in fact, the former look more like airborne torpedoes, like carried by (for example) the Avenger - which I'm sure indicates a shorter range and likely even lower speed, as well. But were the warheads of the PT torpedoes the same size/power as on a DD of the day? The World Wonders...