Being able to choose, "I can surrender/let go" is a form of power. As opposed to people who feel they cannot let go or surrender to source because they are afraid of something, and resist what could happen if they let go too much to let themselves do it.
Also, source is an extension of you, so yes it is good to surrender to source when it just just surrendering to yourself really. But I don't see is as you are handing your power to source, at all. You are using your own power and choice to let go of resistance to your source self.
I know you were asking teal, but wanted to share my perspective in case you found it helpful.