From AIS today: " . . . sorry about the 40nm radius [which I asked for on a "narrow route", though as the width not radius - instead of which they used 10 nm] but on our system we do not have the luxury of specifying this parameter. [I find that extraordinary!] That is a facility only available on the Internet . . . "
So be warned - if you want a wide area, using the "narrow route" method, to bimble around in, either get it yourself; or specify a series of narrow routes +/- 10 nm wide that overlap; or risk missing something important. And the default appears to be, if you ask them, that you have to spot the difference - they don't tell you explicitly that they used 10 instead of 40nm, it just appears in the header to their briefing.
Chris N.