From the article he made contributions starting at least in 99 (so 20 years ago), it will probably be non-trivial to remove all the code he has previously written.
Even if you could remove all the code that he has claim too, that would only be for a future release, and most commercial users of Linux tend to use older, battle tested releases (especially for embedded products.
His first contribution was in 2002 according to the article:
"[...] as Netfilter substantially existed since 1999, three years before Patrick's first contribution to Netfilter, and five years before joining the core team in 2004."
Even if you could remove all the code that he has claim too, that would only be for a future release, and most commercial users of Linux tend to use older, battle tested releases (especially for embedded products.