This was based on an old study from Firefox 4 Beta when the status bar was still on by default. (The study was in July 2010, when Firefox 4.0b1 was out; the status bar was replaced about four months later in Firefox 4.0b7.)
The "Customizations" number just means that 95% of users had the status bar enabled (i.e., did nothing and ended up with with the default setting) while the other 5% customized Firefox by disabling the status bar. It says nothing about how many users "used" (interacted with) the status bar.
Customization is not a good measure of usefulness. We know that 97% of participants never used the RSS button in the main toolbar in Firefox 4.0b1, but that doesn't mean that they all took the time to customize their toolbar to remove the button.
The "Customizations" number just means that 95% of users had the status bar enabled (i.e., did nothing and ended up with with the default setting) while the other 5% customized Firefox by disabling the status bar. It says nothing about how many users "used" (interacted with) the status bar.
Customization is not a good measure of usefulness. We know that 97% of participants never used the RSS button in the main toolbar in Firefox 4.0b1, but that doesn't mean that they all took the time to customize their toolbar to remove the button.