That sounds like the best explanation. Anyhow, I just saved a bit of time and made a bus connection I otherwise would have missed!
I think Underground gates at St Pancras will always accept tickets with the cross-London marker.
That depends on the break of journey restriction of the relevant ticket.
With a 'Not Underground' ticket then yes.
If your ticket had the cross then wasn't it valid on the underground anyway? Plus it is hard to understand how you would you take advantage of the underground if you have to travel via City Thameslink anyway. The ticket might as well not have the validity and save people money
On checking the same booking engine (Evolvi) I find there are "any permitted" super-off-peaks and off-peaks at £4 more than the "route City Thameslink", and I presume the difference is a payment to LU (but if so why indeed does the cheaper ticket have the cross?). But the Anytime return is a whopping £22.70 more!
Origin Destination Route
CANADA WATER RAINHAM ESSEX NOT VIA LONDON
CANADA WATER STRATFORD LONDON NOT VIA LONDON
CANADA WATER UPMINSTER NOT VIA LONDON
HOCKLEY DAGENHAM DOCK NOT VIA LONDON
HOCKLEY WEST HAM NOT VIA LONDON
LEWISHAM BARKING NOT VIA LONDON
LEWISHAM DAGENHAM DOCK NOT VIA LONDON
LEWISHAM LIMEHOUSE LTS NOT VIA LONDON
LEWISHAM WEST HAM NOT VIA LONDON
NEW CROSS BARKING NOT VIA LONDON
NEW CROSS DAGENHAM DOCK NOT VIA LONDON
NEW CROSS LIMEHOUSE LTS NOT VIA LONDON
NEW CROSS RAINHAM ESSEX NOT VIA LONDON
NEW CROSS STRATFORD LONDON NOT VIA LONDON
NEW CROSS UPMINSTER NOT VIA LONDON
NEW CROSS WEST HAM NOT VIA LONDON
NEW CROSS GATE BARKING NOT VIA LONDON
NEW CROSS GATE DAGENHAM DOCK NOT VIA LONDON
NEW CROSS GATE LIMEHOUSE LTS NOT VIA LONDON
NEW CROSS GATE RAINHAM ESSEX NOT VIA LONDON
NEW CROSS GATE STRATFORD LONDON NOT VIA LONDON
NEW CROSS GATE UPMINSTER NOT VIA LONDON
NEW CROSS GATE WEST HAM NOT VIA LONDON
RAYLEIGH BARKING NOT VIA LONDON
RAYLEIGH DAGENHAM DOCK NOT VIA LONDON
RAYLEIGH WEST HAM NOT VIA LONDON
ROTHERHITHE RAINHAM ESSEX NOT VIA LONDON
ROTHERHITHE STRATFORD LONDON NOT VIA LONDON
ROTHERHITHE UPMINSTER NOT VIA LONDON
SHADWELL RAINHAM ESSEX NOT VIA LONDON
SHADWELL STRATFORD LONDON NOT VIA LONDON
SHADWELL UPMINSTER NOT VIA LONDON
SHENFIELD BARKING NOT VIA LONDON
SHENFIELD DAGENHAM DOCK NOT VIA LONDON
ST JOHNS BARKING NOT VIA LONDON
ST JOHNS DAGENHAM DOCK NOT VIA LONDON
ST JOHNS LIMEHOUSE LTS NOT VIA LONDON
ST JOHNS WEST HAM NOT VIA LONDON
SURREY QUAYS RAINHAM ESSEX NOT VIA LONDON
SURREY QUAYS STRATFORD LONDON NOT VIA LONDON
SURREY QUAYS UPMINSTER NOT VIA LONDON
WALTHAM CROSS SHENFIELD NOT VIA LONDON
WAPPING RAINHAM ESSEX NOT VIA LONDON
WAPPING STRATFORD LONDON NOT VIA LONDON
WAPPING UPMINSTER NOT VIA LONDON
WHITECHAPEL RAINHAM ESSEX NOT VIA LONDON
WHITECHAPEL STRATFORD LONDON NOT VIA LONDON
WHITECHAPEL UPMINSTER NOT VIA LONDON+Not Underground means that travel is allowed across London but only by Thameslink or DLR
On the back of tickets one is told that the Maltese cross symbol indicates that transfer across London on the Underground, Thameslink or DLR is permitted. Surely that is, itself, mutually exclusive with a route of 'not Underground'? It's almost as if the ticket is routed 'not Underground, AAA Underground' (or 'Not Underground Plus Underground', a la HS1 routes). I can appreciate what the intent is, but the Maltese cross symbol is flawed in this respect.
Another way of doing this would be to have something like "ZONE U23*LONDN" as the route, e.g. as for this fare from Kingston to Slough, which I think is intended to be used on the District Line between Richmond and Ealing Broadway: