This is all meaninglessness to the average passenger, three or six different fares for the same journey via Slough, Paddington or direct with ticket, oyster or contactless.
There is no way of travelling to Reading with Oyster.
If you use a paper ticket the only available route is "not via London".
Contactless only has one route, the default route. But if you travel via Paddington and touch out at one set of NR barriers, and in at another, you will be charged for two separate journeys.
The choices on this journey really aren't that complicated to be honest.
Why is the public not better informed about all this
TfL want to have PAYG available for all their services.
Paper tickets (or their digital equivalents) won't be eliminated anytime soon along this corridor.
In those circumstances it's difficult how the situation could be made much simpler, other than the addition of a route "+Via London" option for paper tickets. Or extending Oyster to Reading, but that would be very challenging from a technological perspective.
I can now see why people can end up with a criminal record just for getting on the wrong liveried train.
I'm unsure how that has anything to do with the example at hand, where it's simply a case of different ways of paying for your journey?
Yes, people aren't always clearly told that they're buying a ticket restricted to one train (i.e. Advance) or to one company (e.g. GWR only). But that is a separate issue.
Could someone please explain NR-NR OSI at Paddington please.
There are Out of Station Interchanges (OSIs) between certain nearby stations (Paddington NR and Paddington LU are different stations as far as Oyster/contactless is concerned). These mean that two journeys are 'joined up', provided you touch out at one location and in at another, within a given time period.
There is an OSI from Paddington LU to Paddington NR, and vice versa. However there is no OSI from Paddington NR to Paddington NR, meaning that if you exit one set of NR barriers at Paddington and re-enter at another set of barriers, you will be charged for two separate journeys.