The linked dress is from 1885 (19th century) and the linked Wikipedia article says it was a movement in the late 1800s. The point was that it lasted as fashionable for several decades in the 20th century (as in it stayed in fashion, women's fashion at that, for 40 years). The article used (and still uses) a slash rather than a dash, which carries the implication that Victorian (which officially ended in January 1901) and the century are referring to the same thing, not a timescale.
Frankly I've never been all that fond of using "xth century" over "__00s" and would convert it to use those