With reference to the original post I'm firmly in agreement with Jope, the relevant facts are known i.e. Yannes had left C= after the SID was completed and that he never worked for Hi-Toro/Amiga.
What I think might have happened is that this quote (or one very similar):
Ensoniq is one American manufacturer that understands the value of building custom chips.
Founded in the early '80s by some engineers from Commodore
[Bruce Crockett, Al Charpentier, and Bob Yannes], Ensoniq's first product
(a software drum machine) was aimed at the home computer market.
Bob Yannes, on of Ensoniq's cofounders, was responsible for designing
the Commodore 64's three-voice synth chip. In 1982 he designed a portion
of a PC that was similar to the sound synthesizer that ended up in the Amiga.
It was this chip the 'Q chip'. And Paula was born.
was misread and chinese whispers took care of the rest.
By comparing the info from the Jay Miner interview that DrBong linked and the Amiga's patent application I think it would be fairly safe to say that the Paula chip was designed by Jay Miner, Joseph Decuir and Ronald Nicholson.