And I’m reposting my response:
Actually, what happened in Arelon was that significant change to the environment altered the way Investiture worked enough to interfere with its flow. They had to add something missing (the chasm line) to allow Investiture to flow again.
Ie. Nothing was taken from the Spren - something was ADDED to the environment. Something the Spren are missing.
Or: Odium became fully Invested in Roshar, significantly changing the environment by adding a third tone. This damaged Investiture flow to the Spren because they are ‘missing’ the ‘Odium line’ in their makeup.
I think BAM’s capture had the side effect of completing a process Odium was resisting: Investing fully on Roshar. I also don’t think releasing her will do what people think.