Not really. RS3 is very distinctly the 2013 update that brought EoC and completely changed the look of the game.

Nex released in 2011, while the game was in the "RSHD" phase, which was still part of RS2 (follow on from Classic, the same period that OSRS is built on).

Because only two versions of the game exist now - RuneScape and Old School RuneScape - people do refer to things that aren't oldschool as RS3, but it's not really accurate to do so. To be honest, people don't like to admit it, but I think if you really looked at it most things that came to the game pre-EoC are more like OSRS than current "RuneScape". Nex, curses, initial release summoning & dungeoneering, all that stuff, is far more Oldschool-y than it is RuneScape in 2022.