If a provider is actively searching for a client at that moment, he will most likely place his status as AVAIL NOW.
Not sure why RM includes anyone signed on in the avail now search, but probably because it's worth a shot to inquire. But I'd guess majority will not be available at that moment. Most of us providers will sign on check messages, make changes to profile, or show that potential client that we might be available sometime today or near future if you are flexible.