I saw that, but didn't see an answer in it.

"When I had shaped the baby's spirit to be like my own..."

...? And?

Quirrell describes the series of events, but provides no causal model that I see.

So you think that if Quirrell had tried to make a Quirrell imprint horcrux of any other person the same thing would have happened? The resonance relation is created as a side effect of casting that spell?