You might be right, there may gave been some unfortunate oversight. I'm just offering a little more dimension to your inquiry.
Credits are negotiated. That's how it works. You don't get automatically get credited in the opening titles by asking. Sure, Sirtis could have waived credit in the titles, but why would she, especially if Frakes was listed there?
Maybe because when the episode was put together and credits arranged, they still thought Marina would be a surprise. Everyone knew Frakes was directing, so he'd be around.
Whoopi Goldberg wasn't credited in either GEN or NEM despite Guinan's popularity. It could have been a negotiated agent thing for both actresses for whatever respective reasons.
If it was a ‘only room for one in timing’ I can see Frakes and Sirtis each insisting the other take the spot til eventually tossing a coin. At which point the credits guys give a sigh of relief cos they already have his directors credit to scrub some words off of.
I’m hoping they use this story to seriously question the individualist moral backbone of the TNG era. All that matters is doing what’s morally right and protects the life and liberty of the person in front of us being threatened, regardless of risk. Going back to the decision in I, Borg. Soji is objectively blameless and us the innocent person in front of Picard being threatened. But somebody possibly capable of hurting lots of people should she choose to. It’s gets to the question “How much do you trust Superman?” Give a person the power to kill you and trust they are so moral they won’t do it. Picard may have to make the Hugh decision for a second time with Soji.
IIRC, that was because Goldberg had several Oscars under her belt at the time (The Color Purple, Ghost) and, by SAG rules, would have required that she get top credits in front of Stewart. She didn't want that, as she knew hers obviously wasn't the lead character of the story, so she requested not to be credited at all, out of respect for him and the rest of the cast. At least, I think that's how it happened back then.
That's not true. It's negotiated between agents and producers. Remember Judson Scott held out for first billing in Wrath of Khan and the producers finally decided to just drop his credit altogether.
I believe that is an unwritten rule, probably one that would have caused problems for Goldberg and her agent, but not something that was mandatory according to the union.
Yeah, that would be weird if it were mandated. That should be between the actor and their agent and the producers and studio. Just winning an Oscar doesn't necessarily mean an actor deserves top billing and is thus automatically granted it.
Only their talent agents know for sure; (yes, billing is also negotiated in contract deals, so Sirtis got whatever her agent secured and signed off on it.)
It helps they gave her better dialogue than the typical "I can sense the bleedingly obvious." Although, before the episode aired, I amusingly though there might be a scene in which Narek beams down to the homestead, him and Riker get into a fight with Deanna standing to the side saying "be careful, Will. I sense hostility."
Whoopi Goldberg requested not to be credited for Generations because she knew all the promotional material would focus on her if she were, and she didn't want to overshadow Patrick Stewart on his first movie as a lead. Especially when he was already sharing the spotlight with William Shatner. Not sure why she wasn't credited for Nemesis, though it was likely her wish again. It's in the movie. Guinan and Geordi are sitting together at the reception, Geordi asks Guinan if she ever considered getting married again, she says her limit was 23. Then Worf moans, Guinan asks if he's alright, and Worf answers "Romulan ale should be illegal." Geordi responds "it is." IIRC, he was acting on advice of his manager/agent, who shall we say, was an idiot.