In this case, what was the timestamp recorded on the e-ticket if there were a few seconds between tapping the buy button and the ticket appearing on the phone?
When I make tight connections, I only want to get the ticket when I am 100% sure that I will make the train, and tap the buy button at the moment I set foot on the train!
In this case, how is it possible to buy a ticket for a delayed train waiting for the signal to depart?
If I understand correctly in Switzerland, the ticket purchase timestamp is encoded within the e-ticket itself, and the e-ticket will be generated by their back-office systems presumably within NOVA (Netzweite öV-Anbindung)
So, when you purchase the ticket, the timestamp should be the moment when the ticket is provisioned within NOVA databases, before then being delivered to your mobile device.
So you might physically click "Purchase" at 08:00:00, the ticket will be created by NOVA at 08:00:05, and you will see the QR code on your device at 08:00:07.
If the train was scheduled for 08:00:00, and door closed and started moving at 08:00:02, it is highly likely your ticket is
not valid when scanned.
Since it comes down to seconds, this is why SBB, ZVV and many other öv operators in Switzerland say the safest thing to do is purchase the ticket, and see the ticket acknowledged in your phone in the form of the QR code (or check-in acknowledged for check-in based tickets) before you enter the vehicle itself.
Ticket inspections for E-tickets are performed using a handheld device where the QR code is scanned. The details of the e-ticket on your phone beyond the QR code are not normally read by the inspector unless their handheld device is faulty (this has only ever happened to me once ever in years of commuting in Switzerland).
The handheld device has the live record of the exact second when the train/bus/tram left each station, and the device is able to match the QR code with whether the ticket is valid or not based on purchase time, route, class, fare etc and whether ID should be verified (if you have never had your ID verified in the back office systems.)
It seems like a lot of controls and technology for fare control, but Swiss public transport is expensive. It is only fair we buy tickets according to the published regulations, and if there is a data privacy concern one can buy normal tickets from the machine and not have to worry about QR codes or timing things to the second correctly.