I caught the AI cheating red handed!

[Bman]

A human can get close to this behaviour if the ships move at the same speed:

Ship that is further away makes a bee-line for the planet. The ship that is closer makes a few back-and-forth movements and then moves to the planet so that both ships arrive at the same time.

Of course, that will not put them in the same fleet so I do not know if they will appear in combat in any sort of formation.