Fair enough. That seems harsh to me, but then I’ve never read the conditions (my fault!). I suppose with advances there’s an element of cheap price equalling minimal flexibility, and higher risk. Ultimately that’s the trade off for travelling hundreds of miles, with luggage, for only £20 or £30.
With my legalistic hat on the way to look at that would be to say that all train tickets are expressly sold subject to those conditions (in addition to some limited statutory rights). Anyone buying a ticket is therefore deemed to have understood and accepted them, irrespective of whether they’ve read them.
Therefore if you’re stranded away from home/unable to use your advance ticket to travel, you have no redress, so long as the TOC has discharged its responsibilities to you, both contractual and otherwise. Indeed you should (theoretically) already know exactly what you’re entitled to.
The phrase “you pays your money and you takes your choice” springs to mind. As does “If you buy cheap, you get cheap”.