Seems like the playerlist doesn't update players level as often as it should.
I was also walking around Classic's overworld, pretty normally without warping or anything unusual, there being no gmap update and suddenly it seemed as if all of the npcs within a particular level had been merged with other npcs, I entered an inside (would have been scripted setlevel2 rather than a warp link) and all of the npcs within that level didn't have onCreated called Clientside.
Seems like the playerlist doesn't update players level as often as it should.
I've noticed that too. I was helping a friend and told him to go to his house, and had my cursor over his name in the player list. I didn't even know he went to his house for five minutes until he pmed me and told me he was there, the player list never updated his level..