As per the definitions, the thrower remains “the thrower” until the result of the pass is determined.
So this rule is saying the thrower can only call a violation as per 2.7 if they still have the disc.
The other reason a player can call a violation as per 2.7 is if, for example, they are trying to catch the disc and a non-player within 3 metres of the sideline means they are unable to make the catch.
Hope that helps.