2. Developers think for themselves and aren't always "double agents".
I don't think the situation is quite as binary as this suggests. Even assuming that developers are consistently doing what they believe is in the best interest of the project, their employers may benefit from being able to encourage them to consider the items which are the employer's priorities. Developers don't have unlimited time, and if they have to choose between two worthwhile projects and one of them is of interest to their employer, it's likely that's the one they'll spend time on.
I don't think the situation is quite as binary as this suggests. Even assuming that developers are consistently doing what they believe is in the best interest of the project, their employers may benefit from being able to encourage them to consider the items which are the employer's priorities. Developers don't have unlimited time, and if they have to choose between two worthwhile projects and one of them is of interest to their employer, it's likely that's the one they'll spend time on.