So I've posted on the other thread about this, asking if anybody is assured about the trigger. Seems nobody did, so here I am reporting it as a possible bug.
I'm also kind of frustrated because I've repeated Gorsky Core City questline and Foundry's questline like 6 times already, back and forth and sometimes with differing sequence (doing two Gorsky's quest first, then finish Beast fight. Or exhaust Dan's dialogue after Foundry's questline, then finish Gorsky's quest, then talk to Dan again. Etc etc), none of them allow my character to bring up Gorsky's wanting to wipe out the Black Crawlers to Dan, or bring up Dan to Gorsky. Even after I wiped the Black Crawlers, I still can't talk about Gorsky to Dan.
Perhaps I've messed up the trigger? I remembered I manage to trigger Dan's dialogue about Gorsky but can't remember if that happens whether I've finished Foundry's questline or Gorsky's questline or both, but I did triggered it in my first playthrough. Seems like we have to get Gorsky to talk about his past, but that just can't happen for me. Seems like because in this playthrough I immediately asked for GMS Compound Keycard when he decided to close it for good, instead of doing so after talking to Quinton? My first playthrough I didn't ask for the keycard until his Core City questline was done, if that helps.