The last time with the giants it was a tactical move. She SS them to crowd control them basically to give others a few seconds to get ready. She doesn’t need to concentrate to hold them and she can release them at will. However, any caught will be ‘processed’ and sent back to incarceration (taterus) and she has no control how long that takes or stop it from happening. It was stated early on by Myria that the OD babies aren’t subject to the last rule. They don’t belong in tarterus so they can only be held indefinitely without going tarterus.