Firstly, Sony sells such highly specialized lens dozen times less than Canon and Nikon so they want to nake it profitable. The law is simple - more production - less cost.
Secondly, i assume you are the real user of this lens and lensscore (and other one-number* ratings) data correlate with you experience?
As far as i know, real users of 4/500 and 2.8/300 has different opinion, not matched with lensscore.
There is some on dyxum.com forum.
People i know tested 4/500 with Canon and Nikon counterparts as wild-life lens.
It was few years ago on real-life with 22-24mp bodies.
Only significant flaw of the Sony 4/500 for wildlife and photorep usage they found is a little smaller magnification on closest focus distance. Sharpness and CAs even on infinity (landscape) was on the same level.
Anyway, one-number-score is integral value and sharpness is only part of it.
For wildlife shooter maximum magnification will be much significant than corner sharpness, for example.
But how we count all this "score" center sharpness and sharpness distribution across the frame, - 'cause we have also CA, flatness of the fieild, coma, vignetting, flare-resistance (better for Sony 'cause much less lens lements due lack of IS) and so on, to say nothing 'bout weight, IS, focus...