This is a huge noob question, but does a 24 fret bass guitar have a 35" scale neck, or not? How does it vary between every bass? How is it labeled?
Scale length is determined by the vibrating length of the string, not the number of frets per se.

Its the measurement between the bridge and the nut.

short = 30"
medium = 32"
Standard = 34"
Long = 35"
Extra-long = 36"

And a 21 fret bass can be a standard scale and there are rare 24 fret short scale. So it does vary between manufacture and bass model.