It’s not normally stated and, as you’ve said, not many people will want to stand as away supporters. They’re trying to make a point here I think, which will probably fall flat. They’ve provided safe standing now at Southampton for the majority of away fans, so have given a small block to cater for the minority who can’t or don’t want to stand. Most people will avoid buying in that area, but if/when they are the only seats left, obviously anyone wanting a ticket will buy in there, who may well then stand up.
So it could create a situation of our fans in that block arguing between themselves about sitting/standing, with the stewards looking on with complete disinterest and it causing a problem rather than being the intended solution.