Which as you've quoted, requires reference to the terms on which a travel ticket is issued.Er, it is.
(2) In these Regulations—
(a)any reference to a “valid travel ticket” is a reference to a travel ticket in a person’s possession which is valid for—
(i)the day and time of the journey that person is making, has made or intends to make;
(ii)the train and route used for that journey;
(iii)the age of that person;
(iv)use with any rail card in the possession of that person which they are entitled to use for that journey;
(v)use in combination with any other travel ticket in the possession of that person which they are entitled to use for that journey; and
(vi)the class of travel used by that person; and
(b)any reference to a person leaving a train includes a person present in or leaving—
(i)a station, having left a train arriving at that station; or
(ii)a compulsory ticket area, having left a train arriving at that compulsory ticket area.
(3) Where the terms on which a travel ticket is issued require the holder to produce on request any other document(11)when using that ticket for travel, any reference in these Regulations to a travel ticket includes such a document.
I think any further discussion of this point probably needs to take place in the split-off thread.