I don't know if I agree with the term "dog whistle" here.
A literal dog whistle is a whistle that makes a sound at a frequency that can only be heard by dogs (and not humans).
A political "dog whistle" by definition is a gesture or phrase that conveys a hidden meaning only to a particular group, but is otherwise undetectable by the outgroup.
Musk's salute is the literal opposite of a dog whistle. It is directly perceivable as a racist gesture by, well, everyone.
The notion that Musk used the salute to (secretly) convey his hatred for Jews or affinity for Nazis is absurd.