Here is a simple answer: I never heard about ShadowCoin before. a) If your ShadowCoin is really great and has value then why are you agreeing to destroying it? Just continue to work on it. b) If it is doomed to fail then why would it be saved at the expense of Darkcoin investors?
No one has agreed to anything. This is just a proposal from Eric, as far as I know no one in the SDC camp has accepted it. I just find it convenient this doc hits when ZK Snarks is in private testnet. I don't think any merger would benefit SDC until ZK is released and the market reacts accordingly to find its price point because that is the true value of SDC.
To put it in perspective, this would be like Litecoin coming to Dark a week or two before the release of Masternodes and offering to merge with DRK. It might sound good initially but may not benefit Dark long-term at that point. I think if a merger were to happen SDC can get a better concession if the SDC camp just waits a few days.