Hi,
It depends what you mean by get by. Will they survive and do well, yes I expect they'll be fine, although some fish seem to prefer to have the outside bottom of the glass painted so they feel they're actually at the bottom of the water. I think the Transcriptus, spending most of their time near the bottom, might be more comfortable with that, but I'll let others weigh in if they've kept them on a bare bottom. But overall, I don't see why you couldn't keep them with a bare bottom.
But personally I would add a thin layer of substrate just for looks. I've kept them over sand or crushed coral and I think their color looks better with that for contrast. They might look particularly nice over black sand actually. In general, I have found the Tangs I've kept (Trascriptus, Calvus, Eretmodus, Xenotilapia and Cylindricus) have always done fine with a single weekly water change, even with somewhat heavy feeding, so unless you're adding a ton of fish or mixing in other species, I think the bare bottom tank for these is unnecessary. Just my thoughts.