As pointed out in a recent video posted by Mr Matty Plays, the conversation system in Fallout 3 and Fallout New Vegas wasn’t exactly perfect. In fact, it was fairly awful in places. At times, the game would often grind to a halt while you spoke to someone, before resuming business. Matty himself even mentions that quests would break on him because of mid-combat dialogue. So yeah, that needs to be fixed in Fallout 4.