L2J Server

I was wondering , how do people that update the datapack and the server (like they're doing now on Epilogue) know what to add? New NPCs e.t.c. They access the pawnviewer?

P.S.: Sorry if this question isn't appropriate but I'm just curious

some info is taken from client (new npcs, new skills, etc..)
and some is sniffed from retail packets or just taken from retail