A couple comments....

First, if you are using "Auto-Download", where Maemo Mapper automatically downloads any of the maps that you need, then the "fuzziness" is controlled by the "Download Zoom Steps" setting, which can be set on a per-repository basis via the "Manage Repositories" dialog. This setting controls which levels Maemo Mapper "skips" downloading.

Example: If "Download Zoom Steps" is set to the minimum level, then every zoom level is downloaded as necessary, but if set to the second-to-lowest value (two bars), then only the even zoom levels are downloaded, so if you are at zoom level 5, then Maemo Mapper will (automatically) download zoom level 6 instead. This saves space because (in my opinion) you don't need the accuracy of every single zoom level - having every other zoom level is sufficient. You can, of course, set it to 1 bar in order to force Maemo Mapper to download every zoom level as needed. Again, all of this only affects Auto-Download. Manually downloading via the "Manage Maps" dialog is not affected by the "Download Zoom Steps" setting.

Second, when you say "precious few checked," I think you're referring to the "Zoom Levels" tab of the "Manage Maps" repository? That tab doesn't list which zoom levels are downloaded or "enabled," but rather which zoom levels you want to download (or delete) manually at that moment. It doesn't affect Auto-Download.

Hope this helps.