Correct. You also get more backstory about the Mercs; one of them was ex-IRA, for example. And there's a whole chapter about Riggs racing two other cops to Vegas as a bet.
The film itself nearly had a very different ending, as Riggs was originally going to retire and move away from LA.
The movie is GOAT-level, with some of the best dialogue of Mel's career.
Riggs, "I do it real good, you know?"
Murtaugh, "What?"
Riggs, "When I was nineteen, I did a guy in Laos from a thousand yards out...head shot in a high wind. Maybe nine or ten people in the world could have made that shot.
It's the only thing I was ever any good at".
And my personal favourite,
Murtaugh, "God hates me, that's what it is"
Riggs, "Hate him back, it works for me".