Befor September 18, 2013 when Cipsoft implemented version 10.2 there were bosses in Tibia like Fernfang, THe Evil Eye, vampire lords, Dharalion, Man In The Cave, General Murius etc. Some of them drop rare items, most of them not. Mechanism of these bosses is simple - after some time (for example after 10-15 days counting from last kill) boss appears and when players meet him, the loot belongs to the one, who dealt the highest damage.
With version 10.2 Cipsoft implemented new bosses:
- White Pale
- The Welter
Summary eight new bosses.
In that times, these bosses had completely new mechanism - in many cases they had special abilities and what is more important - thanks to the reward chest system - loot for everybody. These bosses were also the first random bosses where participation was the thing that decided who win the best loot, not only damage.
All of these eight bosses has the same note about new AI on Tibia FANDOM. I checked the meaning of AI and I guess that the author of this sentence meant "artificial intelligence". I think that it is about the completely new mechanisms of the bosses for that times (to kill Zushuka or Shlorg you have to do a small task before, just an example), and reward system. Even if bosses don't require to do any task, still about the best loot decides participation, which seems to be "more inteligent" than "best damage wins".
With implementing version 10.7 in Tibia appeard third mechanism of spawning - the particular monster among the respawn has ?% of chance to be replaced by the boss during spawn. In 10.7 we could meet with this mechanism in case of Crustacea Gigantica on the Seacrest Serpents grounds, but soon it was also done with bosses. To kill bosses like Burster, Mahatheb, The Mean Masher etc. you have to kill the respawn all the time and prey for luck :P
Nowadays "One of the eight bosses introduced with new AI." seems to be quite outdated and that's why probably you weren't sure, what exactly it means.