I don't have a Syn Custom, but I have never heard of a warranty like that in 35 years of buying guitars.Maybe a good place to ask this quickly. When I bought my syn custom-s it said "Schechter warranty only for string gauge "9-42" but came with "10-46" and syn uses 10-52...so technically I can't use any other gauge than 9-42??
I mean, I can see not warranting a non-floyd nut if you put super heavy strings on it, but this seems odd. Do you have a pic of this?