More fare anomalies from Oval

I am now checking some fares from Shepperton and an alarming amount of anomaly is found:

Travelling on NR only:
Shepperton – Waterloo (NR): £10.60 / £7.40
Shepperton – London Bridge (NR): £13.40 / £10.10 (it triggers the via London Terminals fare because of the OSI at Waterloo?! but it still remains at the default fare at £10.60 / £7.40 if travel is NOT via Waterloo, for example, by changing to Thameslink at Wimbledon?)
Shepperton – Blackfriars (NR): ditto
Shepperton – City Thameslink: ditto
Shepperton – Farringdon: £13.40 / £10.10 (both the default and via London Terminal, but there is also an “Avoiding Zone 1” fare ending in the very centre of Zone 1?!)
Shepperton – St Pancras (NR): the same fare as to City Thameslink
Shepperton – Kentish Town: £13.40 / £10.10 (both default and via London Terminal, another cheaper avoiding Zone 1 fare is also available)

Avoiding zone 1, for example, changing between West Hampstead (LO / LU):
Shepperton – West Hampstead (LO): £8.60 / £6.00
Shepperton – Kilburn: £14.00 / £10.20 (default route, no avoiding Zone 1 fare available)
Shepperton – Willesden Green: £12.00 / £8.80 (avoiding Zone 1)
Shepperton – Neasden: £14.30 / £10.40 (default route, no avoiding Zone 1 fare available)
Shepperton – Wembley Park: £11.40 / £7.90 (avoid Zone 1, but cheaper than Willesden Green?!)
Shepperton – Preston Road: £15.00 / £10.60 (default route, no avoiding Zone 1 fare available)
Shepperton – Northwick Park: £11.40 / £7.90 (avoid Zone 1)
Shepperton – Harrow-on-the-Hill: £10.70 / £7.90 (avoid Zone 1, but even cheaper?!)
Shepperton – North Harrow / Pinner: £15.70 / £10.90 (default route, no avoiding Zone 1 fare available)
Shepperton – Northwood Hills / Northwood / Moor Park: £16.20 / £11.00 (default route, no avoiding Zone 1 fare available)

Can anyone help me to check what is happening in the above fares?