Again, the primary is not the general. Are the people who voted Biden here going to not vote for the dem candidate? Would some of the Bernie voters going to vote dem who wouldn’t vote for Biden? Talking about the primary in reference to the general isn’t very useful.
Whatever they decide, they’re going to put a lot of thought and money into picking the smartest option. If they go Harris AOC, I’m willing to bet that they knew it’d get the most votes.