I doubt anyone is able to take the protected ruins on turn 59 no matter what they do. Except maybe they're egassem and got ten infernos from the start.
It is my intention to ensure that Ancient Ruins always
get somethign protecting them for these exact reasons.
However: three shielded robohulls and a drydock nearby can take a Sentinel early, I've done it around turn 50 more than once, never with Egassem though, needs a research species that can switch easily. I do however suspect that for the AI to do it it would've been unprotected and I do think that's off (Sentinels can't spawn close to a homeworld, ruins can, it needs tweaking and Ancient Guardians are part of that plan)