Er...uh...well....umm....meh...<cough>....
my bad....I am guilty of mis-reading my own spreadsheet!

Serves me right for trying to surf & watch football at the same time (damn those Seahawks...).
Most of the basses I measured are indeed closer to
equal centers, except the Fender Jazz 5 is equal gaps, and the Alembic 5 and Peavey Cirrus 5 are equal nothing...perhaps poorly cut nuts.
CTC=center to center
ETE=edge to edge
Going from low to high (fat to thin strings) in inches on the digital caliper, each and every gap measured precisely...
Stingray 5
CTC: 0.365-0.360-0.364-0.351
ETE: 0.252-0.272-0.298-0.302
Ken Smith 5
CTC: 0.363-0.357-0.345-0.339
ETE: 0.248-0.264-0.273-0.283
Warwick Thumb 5
CTC: 0.371-0.364-0.361-0.361
ETE: 0.252-0.268-0.284-0.304
Peavey Cirrus 5
CTC: 0.365-0.370-0.350-0.388
ETE: 0.246-0.276-0.276-0.332
Alembic 5
CTC: 0.390-0.391-0.377-0.346
ETE: 0.272-0.297-0.303-0.290
Fender Jazz 5
CTC: 0.423-0.413-0.391-0.371
ETE: 0.300-0.315-0.315-0.315
The guitars I have here now seem to be all over the place...
1993 Les Paul Studio (closer to equal centers)
CTC: 0.273-0.284-0.284-0.277-0.277
ETE: 0.232-0.253-0.262-0.262-0.265
1979 Les Paul Deluxe (closer to equal centers)
CTC: 0.263-0.263-0.268-0.268-0.277
ETE: 0.222-0.232-0.247-0.253-0.265
1992 Fender MIM Strat (closer to equal centers)
CTC: 0.240-0.275-0.279-0.272-0.262
ETE: 0.199-0.244-0.257-0.257-0.250
1995 Ovation acoustic (closer to equal gaps)
CTC: 0.284-0.278-0.269-0.262-0.251
ETE: 0.236-0.239-0.240-0.242-0.237
...but note that #1 none of the guitars have equal spacing (gaps or centers) except the Ovation and #2 the defining characteristic of the electric guitar nut spacings (as opposed to the basses) is a narrowing of the gaps for the two heaviest strings. This alone makes the guitars closer to equal-centers (if you calculate the std dev of the measurements), but they truly are not equal centers (nor equal gaps).
Clear as mud...