Here are some general existentials:
An island volcano exists.
There are uninhabited planets.
Faithful husbands exist.
Unicorns do not exist.
There aren't many chess players in Bagdad, Arizona.
Each of these is expressible salva significatione et veritate (without loss of meaning or truth) by a corresponding instantiation claim:
The concept island volcano is instantiated.
The concept uninhabited planet is instantiated.
The property of being a faithful husband is exemplified.
The property of being a unicorn is not exemplified.
The concept Bagdad, Arizona chess player has only a few instances.
Should we conclude that every general existential is expressible as an instantiation claim? No. 'Everything exists' is a true general existential. It affirms existence and is not singular. But it does not make an instantiation claim. If you think it does, tell me which property it says is instantiated.
Please note that it cannot be the property of existence. For there is no first-level property of existence, and the whole point of translations such as the above is to disabuse people of the very notion that existence is a first-level property.
Addendum, 4:40 PM. The problem arises also for 'Something exists,' 'Something does not exist,' and 'Nothing exists.' Consider the latter. It is not true but it is (narrowly-logically) possibly true. In any case it is meaningful. Can it be expressed as an instantiation claim? If I want to deny the existence of unicorns I say that the concept unicorn has no instances. What if I want to deny the existence of everything? Which concept is it whose non-instantiation is the nonexistence of everything?