Quote - "i so can't understand why the nano window has to be that tiny. just doesn't make sense"

There are a couple of things that have a bearing on this.

The Bryce interface was designed when most people were using a screen resolution of 800x600. In that case, the nano-preview doesn't appear so tiny.

The nano-preview uses the same basic render process as the main window (i.e. it's slow), and if it was bigger it would take longer to render. It's often too slow even now, at its tiny size and with modern computers. If you place a complex volumetric material in a scene with multiple lights, the nano-window will slow to a crawl and most of the Bryce interface will not respond to input until it has finished rendering (sensibly, the option to turn off the nano-preview does respond quickly).

The nano-preview size was a reasonable compromise when it was introduced. Nowadays it would probably be better to have a bigger size option and have it update only on user command rather than automatically.