I have two tickets for today. One is Selby to Kings Cross, with an Itinerary departing Selby at 0911, Ticket Type 'Advanced Single' and Route 'Valid on Specified Hull Trains only'. Fair enough, I understand all that.
I then have another one from London Bridge to High Brooms, with an itinerary departing 1224. Ticket Type 'Advance Single' and Route 'Valid via any permitted route'.
Does that mean I can get any train from London Bridge to High Brooms, not just the 1224 ? I'm only really used to Advance tickets being for specific trains.
This is a more interesting situation than a blanket no, by the looks of things.
There's many places where the idea about booked train only could be placed: most notably the ticket T&Cs, route and restriction code.
When purchasing, the ticket T&Cs brought up are the standard terms which state you can use this ticket on your booked train only, no refunds and no break of journey etc., so this is normal.
Next, your ticket has a route code of ANY PERMITTED which seems to be typical for Southeastern by the looks of things, however is unusual given it differs from practice elsewhere where "AP" (advance purchase) may be put in the route code, or a train operator restriction (e.g. "CHILTERN ONLY"). Typically in these cases, these route codes are dedicated for advance tickets so the description shown in online journey planners would be able to state booked train only, or words to that effect.
Lastly, your ticket's restriction code would have been SA which states "Only valid on booked train and connecting services only". However, this restriction code applies Monday to Friday only.
All put together, this means that a typical advance ticket states "booked train only" in at least three places, whereas your ticket only states it in two places on weekdays and one place on weekends.
To answer this situation more directly though, the conditions present within advance tickets require you to travel on the train services shown on your ticket unless the route states "& Connections". It does not in your case.