Spock calls the Eugenics War the last World War taking place in the mid-90s.
SPOCK: No such vessel listed. Records of that period are fragmentary, however. The mid=1990s was the era of your last so-called World War.
MCCOY: The Eugenics Wars.
So unless Spock was lying, TNG later retconned in another World War after it in the mid 2000s, meaning it's no longer the last world war.
Which then SNW made part of the same series of conflicts as the Eugenics Wars solving the issue.
Spock also says the augments were created via selective breeding (Kirk later says 'controlled genetics'), not modifying their genes, so that's another retcon made in later series.