This summary is not the rule. The rule text controls.
When someone files a class action lawsuit on behalf of a group of people, they have to file it in a parish where it would normally be proper to sue the defendant. In other words, the usual rules for picking the right location still apply, even though many people are part of the case.
When a class action is filed against a group of people (meaning the defendants are the class), the case can be filed in any parish that would be proper for at least one of the named defendants in that class. This gives some flexibility in choosing where to file, since not every defendant needs to have a connection to the same parish.
Basically, this rule makes sure class action lawsuits still follow Louisiana's normal venue rules. It just clarifies how those rules work when there's a whole class of people on one side of the case instead of just one person.