The reason for "levelUpEx" being the way it is, would most likely be because you often also get an achievement after you level up, so the NPC text will disappear instantly after it shows up, in those cases.
On another note: Issues related to AeroLib should be posted in the AeroLib thread, as this bug-report site is really for SRL-OSR.
It's that or if you still feel like posting it here, you should add a prefix to topic title, to make it clear that we are in fact talking about AeroLib and not SRL-OSR:
> [Aerolib] Level up function is ...