The "what the - is that?" ship is most certainly not Seo, it's most likely one of the 4 pursuers that you get a log from just prior to that one.
And they weren't aiming to destroy her ship, but disable it.
Seo has too much plot-armor based on her being high-lighted in the Galnet articles and the expectancy of seeing what will happen from her going off on this lone mission.
CMDRs are meant to follow behind Seo's trail and find out what she already has.
Much like Seo has given the clues to Tanner, CMDRs are now given these clues and are supposed to play the Noir detective sleuth here.
You are not going to be stumbling across Seo in-game, the game isn't set up to give players chance encounters of significant characters mentioned. You won't find Aisling Duval or Zachary Hudson in-game, and you won't find Seo Jin-ae.
"I didn't ask to join this stupid war with the aliens, now I'm trapped in it because of him..." - Seo has a vendetta with Salvation, and no allegiance to the Thargoids. She set out on her lone mission with the goal of finding Salvation. Meaning, if there's a purpose in presenting this narrative (Which there most likely is since they put time into writing it.), then Seo will most likely find Salvation. Or she already has.
Shangdi has ship debris where you obtain shiplogs from a discussion from Seo's pursuers. But that could mean one of them was destroyed there in Shangdi. Which means 1 of the 4 destinations was never reached by the pursuers.
The other is a log from a ship destroyed by some unknown scary space mystery in Ankaa.
That leaves 2/4 who went on from Shangdi. What did those other 2 find? Did they find anything? What was their fates?
Seo mentions her connection with the Thargoids and always being able to hear them; gives credence to the destroyed pursuer ship being surprised by a Thargoid, possibly new type of Thargoid and possibly answering some mind-linked cry from Seo. But Thargoids are fairly common knowledge now, we're in a war with them after all, and there isn't the usual traces of Thargoid caustics.
It seems we don't really have enough info to know for sure what destroyed that ship, yet. But whatever it was, it startled the pilot and was something they had probably never seen before.
Some Guardian construct thing? maybe. Salvation astral projecting himself like some Guardian mind-matrix god? Sounds kinda cool. Maybe?
Salvation had those plans of a 'consciousness upload' thingy (Which he most likely succeeded in building and used upon his death. All the mentioning of it would be pointless if FDev didn't want to bring it into play in a narrative sense.)
Tanner mentioned it as Guardian tech to build a storage device for the mind. So, Salvation was using Guardian tech.
It's plausible, and from the Frameshift Live hints; they've already mentioned that there's something players haven't picked up on yet, and the clues of blue M&Ms, triangle shapes, and the Guardians, there's most likely Guardian stuffs at play here and whatever we're looking for is related to Guardian tech and Salvation.
But we have mostly speculation and no real trails to follow after the destroyed pursuer ship.
What was that pilot so bewildered by?
An Azimuth facility with an access port for a primary - what?
How and where would Salvation build this Guardian storage device?