I may be misreading what you are talking about here; if you're talking about character A describing character B when character A has only just met character B and does not yet know character B's name, how does the reader know character B's name ? Is that something set up elsewhere in the story ? I thought you were talking about writing with a single viewpoint character.
Nah, bouncing between characters while restricting the character to their own knowledge is where i gets awkward. For instance I introduced a POV character about 70 pages into a story. The main characters had shown up on her doorstep and she was listening in via spell to find out who was there. At that point the characters were, Her Uncle, male voice, and female voice with odd accent. To anyone who had read the previous 70 pages they knew these characters by name, but the character didn't. Was a little awkward.
