That is the statement that contradicts causalty, yes. Again, my point is that Jack's wife's death must have happened after Angel's "chairing", and therefore cannot have caused it. Even if Angel did actually do something to her mother, whatever it was can't have been severe enough for her to agree with the chairing, as evidenced in Get to Know Jack.

While there is little hard evidence one way or another whether Angel actually did do something drastic to her mother, I would argue that Occam's razor points to Jack simply lying as the most likely explanation.

Beyond this, my personal pet theory (which I have no evidence for) is that Jack's motivation for chairing Angel had nothing to do with her Siren powers, but rather he wanted to be the sole object of worship (that God complex again) and was jealous of the attention his wife and daughter were giving each other instead of him.