The 1275 ns full-scale delay covers a useful range for board-level timing alignment — think skew compensation across clock-tree branches or generating delayed trigger pulses. With 256 taps you get about 5 ns per step, which is fine enough to align digital edges within a single logic-family gate delay. The first tap comes at 16.5 ns, so the minimum programmable delay is not zero; account for that offset when budgeting the timing window.
There is no LTB window to track, and no forced last-time-buy risk for new designs.