It is absolutely normal that the BF-maps can't be zoomed. They are automatic random-generated, so there arn't automap-files for this maps in the different resolutions.
It isn't a Bug. <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
No, you're wrong. Everything can be programmed. If Larian can program random dungeons, then they can also program maps for those dungeons, at any resolution.
A bug is something the developer didn't intend to have, but accedentaly came up. I'm fairly sure Larian wanted to zoom BF-maps. If it isn't a bug, then that means zooming created alot of performance problems or something like that... But I doubt that.