I believe that DfT regulated Off Peak/Super Off Peak tickets cannot be restricted in such a way, but some Off Peak/Super Off Peak tickets, such as those which are TOC Specific (like some of London Midland's) are not regulated whatsoever and can include whatever Break of Journey restrictions they like.
I don't think this is correct. LM *did* restrict their Super Off Peaks in this way but now do not, and I'm pretty sure them being caught out as not allowed to do it (like VT and their naughty evening peak restrictions north of MKC) was the reason.
Do you know of any tickets you can cite with such a restriction?
Off Peak *Day* Returns can have both directions BoJ restricted (but usually don't, as the risk of reuse is near zero).
--- old post above --- --- new post below ---
I don't believe First Class fares are regulated either so that could theoretically have BoJ restrictions or whatever else applied to an off peak return.
Correct AFAIAA, but we are talking about Standard fares here, are we not?