Taking A Taxi On Motzei Shabbos

If you are in Israel after Shabbos you might take a bus or a cab and the driver has not yet made havdala. The question then is may one benefit from the melacha of the driver [we know that it is forbidden to derive benefit from chilul shabbos]?

Rav Yisrael Yaakov Fischer [אבן ישראל ח"ח סי' כ"ה] had an interesting rationale to permit it. When one makes havdala he is separating between kodesh and chol, but once a person already did melacha before havdala it is already chol for him and he is no longer obligated in havdala. Thus it would be permitted for a person to benefit from his melacha because it is not called chilul Shabbos anymore. The first chilul Shabbos took him out of Shabbos.

I was wondering, that according to his logic if one does melacha before havadala it would be FORBIDDEN to make havdala because it would be a bracha li'vatala. How can he say bein kodesh li'chol if it's no longer kodesh?

But I really don't understand what he means because EVERY TIME we make havdala it is no longer kodesh because we already made havdala in maariv when we said אתה חוננתנו.

Food for thought....