Good one, Taxydual! I often wonder similar thoughts myself when wandering round the city... Sort of 'chavnic' cleansing? There are a lot of webbed feet around here.
I can't remember what yields were posted against both targets, although I can say that they were definitely different, so the separation of the targets and different yields seem to suggest that a backup approach may not be on the right track after all. If I remember correctly, the larger yield was not for the city centre.
And this is the crux of the issue - what was more important than taking the city itself out? Or what was a harder nut to crack?
The other thing to bear in mind is that the map was not dated, so I don't know if this has any bearing on this particular conundrum. The 12Grp underground bunker at RAF Watnall closed in 1961. The RSG closed somewhat later than that.
Sorry I can't help with Stoke.