Well, I don't think they got it right. The definition in Harv's link is much better.
Really? Consider this definition from Harv's link:
Act Of God An event which is caused solely by the effect of nature or natural causes and without any interference by humans whatsoever.
On this particular planet there's arguably little if anything left that fits that bill. Even those phenomena that once upon a time might have easily qualified have now been 'contaminated' by human activity on a global scale. I suppose you could maintain that the exact location of the effects of those 'acts of God' has not been determined, but the counter argument would use the lack of sufficiently detailed models to explain that. The point of all this being that this line of reasoning won't get you anywhere while discussing the pro or cons of religion or God (two entirely different things, btw).
Anyway, against this background, the use of some sort of 'expectation' in the legal description of 'Acts of God' gains applicability and has the added advantage of being sufficiently vague to allow for wiggle room. That has never hurt when money was involved...
