They shouldn't approach anyone in a job unless he's 100% the man they want. To do it any other way is just hugely disrespectful, to expect a manager to put his current job on the line to talk to them and then reserve the right to say no and leave him in the mire.
I know this is from a few hours ago, but holding an interview is exactly the way they could find out if the manager is 100% who they want. I don't see it as being disrespectful at all, just thorough, what other job just hires people before even talking to them?