I dont think that the devs are unable to follow the alphabet order correctly.
So if they used it (as it looks like to nearly 100%), I do not think they made a misplacement there.
Imho, there really are only 3 possibilitires can are realistic:
1.) it indeed is another CIV between Ger and Gre. In this case, and considering the probably white skin color of the portrait, I think only the Goths and the Golden Horde would be possible options. All others are even more unlikely to chose for a vanilla civ (even these both are, considering that we already have Germany, and it is unlikely they use Golden Horde instead of Mongolia, especially since already Scythia is in place)
2.) the overview also contains multiple leaders from the first DLCs. This could be valid both for Germany/Greece and Spain. Somehow this option would surprise me though, as I wouldnt see any of those three as such an early pick for a second leader.
Also, the possible secondary leaders dont look like being from a totally different time period, which I would have expected if a second leader would have been chosen, at least in cases of Germany or Spain.
3.) there are two leaders of Germany/Greece and Spain, because at the time of the print it was not finally decided which one to take. Maybe they had 2 different concepts that they both liked and it was still open.
Of these three options, I would tend to 3, with a small chance of the Goths being in the rooster.
