That link does not work - try again and insert the picture if you can so we can see what you mean.
I work with the A346 just about every day, and to be honest I can't say I've ever noticed, although they do sit pretty low to the ground, I'll have a look next time I'm in ( but not for 2 weeks tho - on holiday now)
The only reason I can think of based on your description is that aircraft in general fly in a slightly nose up attitude, so then the slight downward angle on the engines would mean that they are able to achieve maximum airflow in the cruise as they would be paralel to the oncoming airflow, which after all is where they spend most of their running time.
Just my thought's.
"She Rolls, 45 knots, 90, 135, nose comes up to 20 degrees, she's airborne - She flies, Concorde Flies"