Searching in Currents often returns posts that have been shared with you or posts that have been shared publicly. Occasionally, these public posts, while interesting, may be from people you don’t know.
The content you share publicly in Currents is publicly searchable -- even if your Google profile isn’t. The content that you share to specific people is only searchable by the people it was shared with. There’s no way to make the content you share not searchable.