This is incorrect. For instance the lead-off batter in the bottom of the second inning of the Atlanta Braves game tonight (4/23), hit a deep fly ball that hit the top of the fence and then bounced into the stands. RULING: Home Run.

The original post is not a home run because it hit the fence, then the fielder, then went into DBT (the stands). It is the fact that it hit the fielder after hitting the fence that made the ball no longer in-flight.

Contrast 2 cases:

CASE 1: Fly ball to left. Hits fielder on head (still in flight), hits top of fence, goes over fence. RULING: home run.

CASE 2: Fly ball to left. Hits top of fence (no longer in flight), hits fielder, goes over fence. RULING: two base award (aka ground rule double).

The OP was case 2.