Especially if your fav game is something like WoW that you probably keep open alongside tens of browser windows with wowhead, youtube, twitch etc. and sometimes multiple other applications. "You don't need more than 8GB of ram for gaming" is maybe true if you're the type of casual single player gamer who launches absolutely nothing on their PC than Steam and then their game of choice. That's not how you play MMOs, and that's not how you multitask on a PC. He also specifically mentioned he wants a setup with 2 monitors, which clearly suggests that websites and potentially streaming will be going on at the same time as wow.
So yes, get 16GB of ram at the minimum, but probably 24GB or 32GB would be preferable for future proofing.
When looking at how much ram you want, you don't look at the requirements of a game. You think what the actual memory requirement will be for everything running simultaneously on your pc, including the game.
PS. As a real life example, I have 24GB in my rig that I built like 3 years ago now. During a downtime (web browser, discord, steam, wow, potentially some other game afk) it needs about 12-14 gb on average. If I actually open more stuff and watch stuff, it jumps to 16-17.