first year phyiscs degree here!
This is correct. A pickup in the exact 24th fret possition will pickup virtually no even but lots of odd harmonics (ie no 2nd but lots of 1st and 3rd). HOWEVER, guitar pickups sample the string over a very long length (I'd estimate a humbucker is 'listening' to at least two and a half inches in length of the string, obviously getting weaker signal further you go from the pickup), and so you wont get a case of a pickup not getting any of a particular harmonic unless its got virtually no thickness (a single coil isn't even close to this 'point' pickup)
Oscilloscopes are good but wouldn't be that helpful in this case as its very hard to judge wave forms like guitar signals (they're very complex). A spectrum analyser is what you want but they're about the cost of two new gibsons plus a bit.
most sensible comment yet.
That's essentially a virtual spectrum analyser with a gutiar pluged in. As I'm sure you can all see there isn't a huge differance between the two pickup possitions but there is a big differance between a bridge and neck pickup. (This program is good but not acurate, for instance the freqency responce 1 inch from the nut should be exactly the same as 1 inch from the bridge but it isn't on that program)
Robert