Are you saying it looks like it's a bug rather than just laziness and an "unfinished" product? I certainly hope so, but I haven't seen anything to suggest it being a bug, myself.
Nah... many things about dialogs have been overlooked... maybe beta testers did not test it enough?
For example in the middle of a war an npc gives you the same lines he gave you back in town. Would it be hard to disable the regular lines for that event?
Or a guard asking me to conjure a bed for him because i once read a +1 conjuration book with my warrior. Would it be hard to comment on my 3 highest skills or skills above 75 for example only?
Or saving the life of an npc and at the same time he gives me the line he casually gave me in his shop. Would it be hard to enable his lines only in his shop?
Also i feel that most npcs are like 2-faced hypocrites or have a personality disorder:P
They ask me to get lost, then comment on me being a dragonborn, they thank me for various things and then tell me to get lost again.
Some seem to be have never been recorded at all... for example the ones for the guilds "recognition". Recognition in general suffers... for example Ulfric or Tulious or Jarls etc after praising me seem to have completely forgotten what i did for them (through their random dialog lines). It's like the fixed dialog with the random dialog lines disagree.
Now in general npcs seem to just randomly pick lines about the skills you have and the quests you have done.