Yes that is correct, by increasing IAS the pitch will decrease and vice-versa. What is being said here is that for the normal and economical cruise speed range on most jets the typical pitch is +2 to +5 degrees, depending on the aircraft.
It is also worth noting that there is a slight reduction in pitch attitude as the flight progresses since the weight of the aircraft reduces and therefore less lift force from the wings is required to provide level flight.
This is more noticeable on long flights.
But even if you put the 757/767 up to Mmo in the cruise, the pitch attitude will not drop to 0 degrees, maybe just a tad under +2 degrees.
Hope this made sense?!
I used to love the smell of Jet-A in the morning...