The other factor was that crews were normally operating at between FL410 and FL450. Since AAR was being done in the high twenties/low thirties the engines burnt more and the groundspeed was less. The relevant pages of the ODM were not looked at in my 7 year stretch on Vulcans, as we just did not operate like that.
According to a friend, operations between 410-450 was an unquestioned Vulcan SOP. The more efficient altitude would have been at the trop. The trop of course was not a fixed level at 360 but would have been much higher at ASI and probably lower at FI.
As 50+Ray stated "AAR was being done in the high twenties/low thirties " which would have been less efficient but in the other sense.
The whole issue with fuel planning was that it was too easy in UK, in peacetime, on simple sorties, not to use the ODM. War planning was a good illustration of how it was frequently done incorrectly. It was a task delegated to the co-pilot, often a very junior pilot. Frequently the wrong speed tables, 240 vice 325, were used. The correct AUW was often used to the target but after the target the off-loaded bomb weight was often converted to useable post-target fuel. It was my job to check and spot these errors (once I had been taught a quick reference check system by a senior navigator).
I am not suggesting any of the above errors applied but just to confirm that ODM practice was a rarely practised skill.