If not FTL travel, it is possible they were sending out sleeper ships with a crew, including or exclusively monks.
Though, it is also possible that the material generated by LUG and others for Vulcan spaceflight is no longer valid with Enterprise.
I imagine when the designers filled in a lot of the gaps for backstory, they did so knowing full well that it could be countered by series or movie at any point.
I've seen evidence in this forum so far that indicates people being peeved that the writers of Enterprise seem to be ignoring the hard work LUG and FASA and any of the other folks generating content for the RPG.
Just my thoughts...
Quack
Salinger/TheDuck
"If it looks like a duck, walks like a duck,
and quacks like a duck...it's gotta be Salinger." -Quack!
"You're living in America/Leave your conscience at the tone."
- Jonathan Larson, Rent