perhaps a typo on the warmoth site. Thats an odd scale for an SG.
Yes I agree or perhaps they are selling a "lookalike" with the fender standard length.
Anyways To the question I further expound. If you have a body designed for a 24 and whatever scale and a neck for 25.5 and the bridge is already positioned it will not work.
Now If the body is blank you may be able to cheat but it wouldnt look right. the Pickups would be differently spaced and the tail maybe too close to the ass or lotso stuff like that.
For example putting a strat(25.5) neck on an SG is just not going to work unless you want to play all out of tune and wacky...which actually is found to be intersesting...for some.
Whats an Epiphone SG's scale? It might be 25.5...I dont know. If so then it would work but just look a little "off" styalistically.
If you want to build a guitar Id say do up a strat, theres gads of parts around for cheap and most will all work together. Plus its 25.5
PS(hardtails are easiest if your making your own body.)
What ever happens GOOD LUCK and watch out for the insidiousness of obbsession.
Have to go turn up the heat-
sincerely
Soupbone.