The default zoom setting isn’t saved with the map or the POI (or at least it’s not supposed to be saved).
It’s intended as a workaround for not having zoom levels for individual POIs, in these 2 cases:
1) Initially displaying a mashup that has only a single lat/lng POI
2) The ‘center map’ link is clicked and there is only one lat/lng POI on the map
You should be able to edit a map and save it at any zoom. I just tried it with a single POI by lat/lng, and it seemed to work for me.
I’m probably not understanding the issue. Maybe you can explain further how to reproduce it, or send a login and explain how I can see it in your blog.