Exactly. In the busy European airspace it is extremely unlikely that you will fly the OFP alternate route or any other programmed route. It just will not happen. All diversions I have done went something like ‘eehhh…fly heading 180 for now’, or a direct to some waypoint in the general direction of the alternate. Followed later on by more sensible direct routing once the controllers have finished coordinating amongst themselves.
Of course, for planning purposes I rely on the OFP figures (if sensible) and take it from there as things happen, using the MCDU as guidance as the situation develops. For example, the decision to divert is just as likely made from a holding waypoint or position well before the approach.That’s a whole different proposition all together in terms of required fuel and routing. For example, the only time I came close to diverting from MXP to LIN was in the hold over VERCE, well south of SRN. In that case I’m far more interested in the fuel required from VERCE and that’s where the MCDU comes in hadny! For that I will use the secondary..