I would say that her promise to return—made in her departure during Heavensward—says otherwise. Imagine if she'd made good on that promise. Where would she go, and what would she do? The answer should be fairly obvious: She'd try to get back to the life she was living before the call to sacrifice was made.
There's also the Louisoix card, Louisoix having died before the Scions of the Seventh Dawn were even formed. Even the part where's he turns out to be not quite dead—being the primal Phoenix and all—he never actually joins the Scions, but is considered an honorary member. So naturally, his triple triad card is a Scion card. If a matter of paperwork, so to speak, is enough to disqualify the Oracle of Light, why not Louisoix as well?
I'm not suggesting that the Lyse and Louisoix cards should retroactively have their "Scion" tribe removed. Rather, I'm suggesting the Oracle of Light should have it added. I'd say even say the same for Ryne, should a Ryne card be added at some point. Even if she's not "legally" a member, she's one in spirit, just like Lyse.
And I'm not suggesting this is some big issue, either. Like I said, it's an innocuous detail. It's a very small thing with little, if any, meaning. Unless it turns out the absurd plot twist is actually the truth, which, well...
The Oracle of Light not being Minfilia would certainly explain it. But like I said before: That's absurd, and I don't think they'd spoil it through a triple triad card.
