Some really excellent points here. But I don't think anybody expects a trial candidate to be fully adjusted on day one, only that they show the ability and desire to adjust. I think you've argued against yourself tho. I know for sure that orchestras aren't interested in players who cannot get into the swing of things relatively quickly. That's part of the meaning of "good fit". It's not an exact fit, but close enough that a player can jive with an orchestra/section style, attitude, ethic, and habits. If the player isn't a close enough fit it won't be a productive relationship.
Learning to do all these things takes experience. Not all excellent musicians have this experience. Some people are more naturally flexible. There are a lot of variables but we're all in the same boat in terms of advantages and disadvantages. And you're right about about standparters needs... But that's why it's a vote. Enough people need to vote against you, it's not dictated by one person usually - tho inevitably there is always a deciding vote. Democracy ***** sometimes but it's better than the alternative. Many times, players are awarded positions despite complaints of members in the section. It's about balance! Every orchestra has its own process... Hopefully it's a good one!