More in depth than I was looking for but thanks for the info. I do think that it could even be a mixed situation where the Preservers dropped some humans at Alpha Cent. but a full-fledged colony came later. It's also possible that the "Preservers" are more than one race or that the uncoordinated activities of multiple races have been lumped together under that umbrella term.
After all, the activities of the ENT-D in "Homeward" could lead in time to a "Preserver-type" myth amongst the inhabitants of that planet.