If we look at how the RB19 evolved over the year, is seams like there is an insatiable desire to ram more air onder the sidepod. RB converge to an optimum, but went as extreme as the chassis allowed.
The underbite lip has become almost a similar device as the W14 wing
This makes me wonder if we see a sidepod inlet that is more a NACA duct on the top of the sidepod than a real forward facing inlet.
Also the underbite lip may curve down to ram more air inder the sidepod or create outwash , like the W14 mirror strut wings do.