Btw, I'm a fan of BvS and WW's intro...one thing I do wonder is: if Lex had old pictures and modern surveillance video of Diana, he obviously knew what she looked like. Yet she showed up at Lex's party and didn't seem concerned he might recognize her. It's probably a nit, but has anyone thought about that?
Eh. Just one of many plot holes for me. I have issues with Diana's "motivation" in DoJ being the retrieval of a 100 year old photo. Sure, it's fine and dandy to be sentimental, but Diana seemed to be really attached to that photo. It's not as though people walking around today don't have doppelgangers in very old photos. There's always click-bait "news" articles about someone looking identical to their great grandparent / random relative / stranger in another part of the world.
And it did seem pretty foolish for her to appear at Lex's party as "Diana Prince" if she knew that Lex had a photo of her as "Wonder Woman" in WW1. Wouldn't appearing at the party looking almost exactly the same (i.e. no blonde wig, no glasses, no loose clothing to disguise body shape) cause Lex to do something if she believed that she was being investigated by Lex? Sure, it's not like Diana has to worry about any private security goons, but if Diana's aim is to live as covertly as possible, then attending a big party hosted (?) by the person seeking to reveal her "true" identity seems like a misstep.
I'll just guess that she knew that Lex was investigating her role in WW1, but didn't have any reason to believe that a billionaire would actually be investigating metahumans (even if he had published the "metahuman thesis" or was involved in that thesis) or herself personally, but rather just the events in which she was involved. For all she knew, Lex may have been investigating Steve Trevor or one of her other allies, perhaps someone who was even a Luthor ancestor.
Still, that plot hole pales in comparison to other plot holes and unexplained character motivations (e.g. Lois retrieving the spear, Lex's plan for Doomsday no matter the outcome of the fight between Batman and Superman, the public blaming Superman for deaths by bullets and bombs, Clark not being fired for continually refusing to do work assigned to him by Perry White, etc).