It not the 'as bad as people think' so much as the 'its not going to be as good as some think' which is being addressed. You cannot have an i5 passively cooled in a tiny case and not throttle at all. A large heat-sink at the back can only deal with so much heat.
Kaby Lake is only a little more thermally efficient going by this -
http://www.tomshardware.com/reviews...7-7700k-i7-7700-i5-7600k-i5-7600,4870-10.html. It's not going to halve wattage versus the SP4.
A proper engineer who knows the maths (
@MrFox?) could actually calculate heat dissipation from the rear heatsink, but a little common sense seems conclusive to me - the surface area of the back of the SP4 is 59,000 mm^2. The surface area of a HS is way more than that (
this one is ~150,000 mm^2 quick calculation) yet it still needs airflow. There's just no way SP5 will be 100% performance all the time passively cooled (unless it's clocked way down). What we'll almost certainly have is SP4's performance, same thermal profile and throttling, only with silent operation and no fan kicking in.