Yea, I see what you mean, but if there was just the episode "The Old Man and the Anomaly" without "The Children of Gabriel", that would have been a different story since "The Old Man" is an alias and "Gabriel" is not.
If you want to be technical, "The Children of Gabriel" is referring to the group, not the specific person. So arguably, Gabriel only has one episode named with him and it's with his alias. Clarke has two episodes with her alias. With "Echoes" and "Ashes to Ashes", it could be argued that it's referring to events within the episode and not character. Really, I think this is all pretty trivial, even as far as trivia points go.