Grail says you need to have completed one of:
51825
51826
[Proudmoore's Parley:50972]

The first two do not exist anymore. WowHead does not list them at all, not even obsoleted.

https://beta.wowdb.com/quests/51826-proudmoores-parley knows about them.
Wowhead doesn't list all quests, sometimes they miss out on rare edge cases, which this might be if not enough players went a specific route. Sometimes they do miss hidden tracking quests that are only completed by actions instead of accepting and turning them in.

It looks like 51825 existed in build 26530, 51826, in build 26567, and 50972 in build 26231, according to wowdb.
Neither 51825 nor 51826 have faction information and neither are recorded by wowdb as fulfilling https://beta.wowdb.com/achievements/12473-a-sound-plan , so I would suspect they were part of the beta and never hit live. If they were alternatives, then the quest text if often different.
If they were in live, then I would expect more information on the alternatives.
But I'm sure @smaitch when they were added to Grail and if they were ever observed after that.