I suppose in the same way owners agree they'd rather be charged for the kWh and not for time, the system designers had to decide "do we want to provide a charging cutoff based on state of charge, or based on the length of time spent charging?" I think the correct answer is apparent – most people in need of change are there too hit a target SOC, absent any promotional plans skewing motivations.Fair enough. And I would not plan to hog a charging spot in any case. But if I plugged in and went shopping and got back to the car after 35 minutes rather than 30, I would prefer not to be charged for an additional five minutes of power. Five minutes of idle charge would be reasonable under such a circumstance.
Owner/driver convenience was obviously not a factor in the UI design in any respect.
I'm in 100% agreement that the myVW app is missing features and not a very smooth user experience, but I doubt we would ever expect see a charge timer in quite the way you're outlining.