Exactly as Double Deuce deduced

!! - units
need to be able to react in the enemy turn certainly, because of the IGO-UGO nature of the game.
Reducing the "quantum" of the turn interval allows finer distinctions, but the overlap would
still be there, as well as the "freezing" of your unit in its end point for the entire enemy phase of the turn. The cost of that is more turns to do the same thing (or game systems with complex interacting sub-phases etc.)
The reaction return fire (and turning) is in there to balance the time overlap of P1 and P2 in a IGOUGO system.
For reaction fires - a unit which wants to turn to point a hull mounted weapon (hull turn) has a much lower chance than a turreted vehicle. Especially if it has moved.
I'll check the turn-to-face code and see if it is using the right sort of chances for hull turns.
But the bottom line is that because of the game system - enemy units
must be able to react.
Cheers
Andy