Two different arguments here.
First...to me it's irrelevant whether the man went out with the intention of doing approaches, or was out doing his thing and saw a girl to approach. I agree with you that it's better to be doing your thing, but to each his own. Who cares? It has nothing to do with what the guy did to himself in the original post.
Second...If you see a girl you want to meet, go up and talk to her. Forget "signals." They help but aren't the be-all end-all and you leave plenty of good women on the table if you only look for them. I don't care about success rate because it's all success. Some guys think "she rejected me, so the conversation was a waste of time." First, I disagree - it's time well spent. Second, it's very little investment. Three to four minutes should give a clue about if she's interested or not. Really, who cares. What matters is are you having fun. You are not going to fukk every girl you meet, so you might as well have fun talking to them. If she's a bytch, that's her problem. (And yes, Virginia, I've gotten laid from girls who didn't even look my way once.)
The problem with strictly waiting for signals and IOIs is it goes against frame. Frame > anything she does or doesn't do. Don't wait for permission. Be a social retard and go talk to her.