I am one of those guys, now. Used to say the FCU/MCP takes whatever the ATC clearance is. Crossed the what
ever, the refined version is the FCU takes the next cleared altitude.
The narrative is faulty.
a) There'd be V/S as the immediate reversion mode
b) Once the ATC issues heading the clear altitude will still be appropriate or modified.
Sorry to say, the inadequacies of the narrative point to an incomplete understanding of what may be unfolding. Does one feel qualified to critique other people's valid technique then?
Try the RNAV to Varna on a busy day and come tell what use the coded constraints were. Triple the fun if working off Jeppesen database.
DWC arriving from the north-east is another good example.
Now that the side-lines are defined, time to look for some middle ground: Whichever gives you less work, IMHO. Fiddling with the FCU can be a lot of distraction! If the VNAV works it's better to use it as designed, without interventions.
Having just said that, once you get busy with something not on the chart (tfc, wx, atc, crm), keeping the FCU set at the next limiting altitude is an effortless measure to avoid paperwork.
Originally Posted by gimbal_error
The FMS needed to be checked/programmed to the very last detail prior the starting the descend. That takes a while. A short term switch onto a different STAR usually ended in some hasty reprogramming with the result of wrong parameters entered. Been there, done that. During the descend it required a close non stop monitoring of the autoilot modes which keep changing all the time. A quick distraction could let you miss an unexpected mode change with interesting results. Been there, done that too. Setting the next altitude restraint manually continuously during descend could be a safety net to avoid a hairy situation.
^^^ This. Engraved in gold with platinum letters.