Adobe dropped the experimental, native 64bit Linux support officially in the mid of 2010.1) Therefore, there was no alternative to the slow but safe 32bit wrapper, provided by the flashplugin-installer package.
But there's life in the old dog yet: Adobe released a new 64bit Labs version yesterday. If you want to use it, you may be interested in some manual installation instructions and/or a 64bit Flash installation/update script for Ubuntu Linux.