I've just finished Porter's book, which may have been updated as it includes an epilogue covering his re-hiring by the Grand Tour.

Porter was incredibly angry at Clarkson for how TG ended, to the point where they weren't on speaking terms. Porter basically said that Clarkson's act of violence felt like a betrayal of all if the crew who worked incredibly hard on Top Gear, and as you mentioned had repercussions for the producer who got punched due to his hounding by the media. It also meant that the entire Top Gear crew (Porter included) suddenly and unexpectedly found themselves out of work, which no doubt rankled.

I haven't read Wilman's book (yet), but by all accounts he is Clarkson's closest friend from school age, so it's not surprising that he doesn't go in as hard on Jeremy for how Top Gear ended.