Which is obviously something not proven either,but just what the GW believe.
The silent grove is a DA comic which is canon for the player in the case that Alistair remain a GW or was crowned king.
now the latter scenario may happen in fact with the scenario of the Loghain redemption means that Loghain soul should be technically "erased" and yet Maric reveal to Alistair that both Rowan nd Loghain souls are still in the fade and that he doesn't wish to return in the mortal world.
Is your choice to make it 100 to 500 you can simply allow the Warden to throw himself out of a window when he is 100 years old
True, it isn't proven, but it is the belief. And it's the belief that is what could cause some Wardens to chicken out, unless they knew it all along and mentally prepared for it during the length of their service.
Um... I'm not sure if the comics can accurately portray a Loghain Sacrifice worldstate in the first place. The comics showed a Warden Sacrifice worldstate. So if that even was Loghain's soul, it is only because he was executed. However, I doubt that was even Loghain's soul. That was probably just Maric's dream world and memories.
I think the theory of soul cancelation comes from the fact that the archdemon's soul does not rise again. If that soul no longer exists to be reborn in a different darkspawn, then the UltSac Warden should logically be destroyed as well. The theory probably also dates back to the time when the Joining was formulated. Tevinter magisters probably calculated this out.
It is not a proven fact, but as I wrote, in order for my point to work it only needs the Grey Wardens to think that their soul will be destroyed, and they do.
It's true that the PoB Hero can choose to die the hard way at any time. That's a good point, and I can't argue that. Still, there are some Heroes who choose not to drink from the concoction, knowing how it was made. Some Heroes also want to be free of the taint completely. I have one Hero who did not drink and wants to be cured, and I have one Hero who drank and only wants to find the cure so he can profit from it.