When the router bit manufacturers refers to a spiral-cut router bit as
up-cut or down-cut, are they consistently speaking with reference to the
router base? Or are they assuming a router-table orientation as opposed to a
hand-held router?

The ambiguity being, of course, that a router bit that cuts away from the
router is down-cut when the router is being hand-held, and up-cut if the
router is mounted under a router table.

Tom