It's all well and good saying what you think of the nose due to its aesthetics but McLaren have the data and hundreds of smart people with terabytes of computing power and streams of wind tunnel figures! They will know what's working well and what isn't.
It'll be to do with the cohesion of all the parts as a unit rather than an individual flaw. Perhaps there was too much emphasis on designing the mushroom suspension fairings and the whole car was built around them, but only they know the answer to that.