I believe this was a change made in an earlier prerelease. Both Nuurag and Master Summoner have always had the capacity to teleport, but were prevented from doing so unless you led them off the level.
I'm not sure that this change ended up being necessarily desirable. OTOH, it does mean that scrolls of monster aggravation and whatnot are actually useful now.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.