I am sure that you know the rules but just to clarify your post for the benefit of everyone - there is no distinction between barried and non-barriered stations in the ticket rules.
Yes, fair point, I should have made that clearer. As others have said alighting short or breaking journey with an advance ticket is fraud regardless of whether a station has barriers or not.
Interestingly though if you are using an Advance ticket, I think I'm correct in saying you
are permitted to go outside the barrier in order to use station facilities (toilets, shops, refreshments etc) at gated stations where you make a booked change of train (as long as you catch your booked onward service, of course). I have certainly never been challenged by barrier staff when I have asked to do this in the past. A break of journey is only technically made when/if you leave the station premises.