Date wise it does, according to Hajdamach production of Caerleon started in 1929. Reading between the lines, Stevens and Williams added more shapes and colours to the range after a year or two but it seems they were not produced for many more years as the fashion changed. Art Deco shapes became much more popular and no doubt the interest in archeology waned a bit after the discoveries in the mid twenties (Tutankhamun) and in 1928 at Caerleon.
I would take with a pinch of salt there being twelve reptile vases, twelve shapes all told seems more likely.
John