Yup! They might be the first game that became large scale to do it honestly. Because their game was getting quite big but they were a Java applet they (speculating a bit) wanted to maintain the fast load times as they added more and more content and get new players into the game quickly.
Plenty of innovation out of Jagex back in the day (sadly not so much now). The founders sold their shares and left the company, the founding programmer started a company where he’s been working on a new game engine concept that’s supposed to make multiplayer as easy as single player to program for, I try my best to keep an eye on it (www.fenresearch.com).