Yes, if you think about it as a pure numbers match up, and to fix the whole you must replace all the source that was taken, and all that was taken is responsible for everyone alive, then it sort of follows that you'd have to wipe everything out to fix the hole.
Perhaps Source is an energy created and consumed over time, and so instead of a zero sum game, Lucian just needs X amount to seal the hole, and you provide enough to get him to X. (shrug)
I do think that this ending was the "best" choice for the world though. I tried all the options (seal hole, become divine, give everyone source, and (Fane) let Godking return) and the others all seem result in obvious problems.
