This is how the system was designed. It is not always possible to require an avatar character, or a specific character, be available when a dialogue is triggered, and delaying dialogues for story events could cause more problems than starting it was the non-preferred character. NPCs can look for specific characters, or avatar characters, but how that is handled depends on how each encounter is scripted.
The distance checks were increased for some situations so it was less likely certain origin moments would be missed, but an overhaul of the dialogue system for D:OS 2 is unlikely at this point.
