"SmartThings Classic" vs "SmartThings (Samsung Connect)"

Already been 3 rounds of Beta Testers

This migration has nothing to do with moving you to the new app.

It is coordinating and migrating all information from your ST account to a Samsung Account. You will continue using the SmartThings Classic app just like the rest of us who participated in the Account Migration Beta. It’s the same IDE, just a new account which can use the same email account you are using now for your ST account.