Continuity mistake: When Steve Trevor is at the Ottoman empire, he is beside a biplane that look like a British one. In the background to his right are a series of Fokker EIIIs, the next shot he's turning to his right, just besides a Fokker... and the British biplane has disappeared. (00:24:23)
Continuity mistake: When Steve and Diana get to London, he is on her left then on her right.
Continuity mistake: At the bar while the bald guy is pointing with the gun, Diana is across the table, but in the next second she is beside the gunner.
Continuity mistake: While WW is training as an adult for the first time she uses a whip to take down an Amazon - one second later she blocks an attack with a sword she didn't have just before.
Continuity mistake: While Hippolyta is dying her hands move on Diana's body between shots.
Continuity mistake: While Hippolyta is dying, there is a sword on a bow which disappears between shots.
Answer: It would be more accurate to say they grow to a certain age then stop aging. Similar to the elves in Tolkien's Lord of the Rings.
jimba