My understanding is that consuming one's soul condemns them to the Void directly. So consuming them is what gave Braccus the ability to call them from the Void. [...]
This is directly contradicted by Wendigo, who wants to get sucked up to escape the Void King, and the same is reflected by countless Black Ring members who seriously scream - and then vanish - if they are consumed.
IF it actually works differently then the entire run of the game gives us a wrong impression. And this means: It might be intact regarding the lore, but it would be horrible game design. The same is true, in fact, if you have such a massive feature built into the game that plays a central role - but you neither can be bothered to tell the player nor make it an actual point in the plot that plays a somewhat transparent role. In all cases this is solved badly.
But the more I think about it, the more I very seriously dislike the entire big fight. It just behaves so different from the rest of the game and, to me, isn't fun at all but just a tactical puzzle - one that behaves different, in a bad way, from what I played in the 100 hours before.
I do really like the game and it is awesome, but this final fight isn't good.
But the core here stands: Given this is such a central aspect of the game I do think that we need to bend whatever moresel we find in the game shows the game does have a problem here. Both regarding lore as well as game design.