Given the suggestive design of the ship, I'd prefer to speculate that in such a case, the Starfleet Antares
was always a transport, and her mission was not altered for the DS9 era. The only "Starfleet Antares
" unit we have to worry about was the Hermes
from Picard's blockade fleet in "Redemption", and it could well be argued that a fleet needed a logistics support vessel, or that any tub with a warp engine and room onboard for a tachyon generator would do.