Hi Alexander,
I think I’m getting what you are after. Starting from Reading, the fares to stations within the zones do follow a certain structure, but it is unique to Reading and I’m not about to create a grid for every contactless only station. The fares to Ealing Broadway [3], and Greenford [4] (via West Ealing [3]), are indeed the same.
The PAYG fares shown on brfares.com are not always correct. This is because it’s the rail industry database and not linked to the PAYG database run by Cubic on behalf of TfL. I can assure you that no fares heading out from zone 1 have ever been off-peak in the afternoon peak. This is because the PAYG fares are single only and the sum of two of them needs to match the Anytime return. Fares for paper tickets are completely different and off-peak fares between Paddington and Reading are indeed valid on Elizabeth line services in the afternoon peak. It should be noted that stations being added as part of Project Oval have had their restrictions changed for paper tickets so that they better match the PAYG structure. This may eventually happen on lines which already had contactless PAYG before Oval, especially if Oval extends the coverage further. We’ll have to wait and see.
Finally, some journeys are defined as being unlikely to be undertaken and so no fares are defined. This is true of Reading to Piccadilly line stations between Osterley and Heathrow inclusive. I imagine the expectation is that you’d use SWR to Hounslow or Syon Lane, or change at Hayes and Harlington for Heathrow. If you actually make the journey then you will be charged a fare, but it might be more than you’d expect.