This kind of makes sense from a balancing perspective. Once you complete the main mission, you can’t fail it anymore, even if you fail to extract. This stops the player from rushing the objective so they can clear the rest of the map stress-free. So you either risk failing the operation or have a much harder time exploring. Completing side objectives as you move along the main objectives seems like the ideal play with these mechanics, and I feel like that’s the most intuitive way to play, anyways.