The only difference I can see (apart from >10km vis required) would be that the pilots that the article is specifically aimed at (if indeed it is) maybe are using SVFR in order to fly <1500 ft over the area thinking, in this case incorrectly, that they are safe from the ANO.
Don't forget, Barney, that the 1500 ft rule also applies to twins under VFR.
It would be interesting to know how many times SVFR clearences are given through LCY.
I have previously asked for and been given a SVFR clearance spefically to allow me to fly below a 1700 ft cloud base over the City of London. The conditions were VMC, but SVFR was necessary because of the 1500 ft rule. Thames was, as always in my experience, very helpful in accommodating my request.