I must admit, travelling around Europe, using the train number to identify your train seems pretty common. Guards/Station Staff will tell you to get train XXXX from Platform Y as well as the time it departs, rather than just time and platform.
It makes it very clear what is your train, especially with reserved seats/tickets etc (which normally have the train number on them).
I feel that SE HighSpeed was a poor testing ground, because it's effectively a 4tph commuter service. Commuters don't need more information. They know what train to get, because they get it every day. This would, however, be useful for intercity and regional services.
Notably in Europe, most commuter services are run as S-Bahns which don't display the train number, because they have a consistent stopping pattern, no reservations, high frequency etc. The usefulness comes when rocking up to somewhere like Brussels Zuid, Amsterdam Centraal or Frankfurt Hauptbahnhof and knowing you need to get a specific train to another European city, or a regional train that only runs once an hour. That's when train numbers come into their own (much like flight numbers - because it's easy to recognise a single piece of information, rather than looking through a long list).