So, I'm a little confused regarding Karlach's ending, as it sometimes seems to be skipped altogether, and sometimes forces you into one outcome:

On my Honour-Mode run, I didn't do the Steel Watch or Iron Throne, effectively skipping the Act-III part of Karlach's quest, as allying with Gortash is easier when you try to beat the game any way possible.
I expected the usual scene on the docks at the end (I blew up Gale), but instead, Karlach's scene was simply skipped, and she showed up to the Epilogue party as if she had gone to Avernus by herself.

Then I repeated this process on another run (not Honour Mode), except this time, I defeated the brain, rather than blowing up Gale. On that run, I was a gith and went with Lae'zel at the end, assuming that, because I once again skipped the Steel Watch and the Iron Throne, that Karlach's ending would be skipped the same way. But instead, she died on the docks, as is commonly expected when going with Lae'zel, as Lae'zel always leaves before Karlach makes her choice.

In both cases, I didn't do the Ansur quest either, so Wyll just remained the Blade of Frontiers on both runs.

So what's the deciding variable here that skips Karlach's scene on the docks? Blowing up Gale? Not being a gith / not going with Lae'zel?