The 2018 reference in "Space Seed" does dangle there, since it seems obvious that any early-21st century Earth vessel predating Cochrane's Phoenix flight would have to be sublight in nature. Of course, FIRST CONTACT seems to have "moved the goalposts" by shifting the third world war from the 1990s to the 2050s, so it seems logical that Bermanian revisionism/retconning in FIRST CONTACT re-establishes Lt. MacGyvers' "2018" sleeper ship reference down the road 55 years to 2063.
If you're willing to accept moving goal posts, why not also move the goal post for Kirk's remarks in "WNMHGB" and in the Berman version he'll say "lost more than a century ago" since the timeline is different...
It would definitely make more sense for the Valiant to have launched later, say, 2073-2113. Ir depends on how much you want to stick to the notion of "over two centuries" relating on the one hand to the notion of the assumed date of "Where No Man Has Gone Before" (2265 -> 2065) and the assumed date of World War III (1993 or 2053) as it related to what Marla McGyver was saying about sleeper-ships being abolished (2018 or 2063) upon encountering the Botany Bay.
Bermanian TREK definitely shifted things quite a bit in the 21st century.