Gii's Model generator created models based on database tables. If you have a table with a boolean column it can have to possible values. If the column can have NULL there is a third option. But that's it.
So things like "does it mean you have to check the checkbox" is controller logic. The database can have two or three values: false, true and maybe NULL. So these are the values that should be possible to use in the model class. By default $strict is deactivated, so it works fine with CActiveForm generated checkboxes which submit values "0" or "1" which then will be conveniently converted to false or true.

> does it mean you have to check the checkbox?

This is controller logic. E.g. when accepting terms of service. But that is a special case in which you can use
```php
array('attribute', 'required', 'requireValue' => 1)
```
This is no database issue but solely something that you want in your special case. The database can still hold a boolean false -- and so the Model should be able to. Eventhough gii is just guessing and trying to give you a good starting point, i believe you should try to be as close to the table of which the class will be created and not on special cases that may rise to some persons