If you ask what justifies a deflationary account of truth, doesn’t that reveal an implicit isomorphism within the justification thus collapsing the account into a traditional correspondence theory?
You're right these 2 rival theories of truth do sound very similar in nature such that many people regard Tarski's semantic theory of truth as deflationary while Tarski himself regards it as a kind of correspondence theory. The subtle difference can be hinted according to SEP reference here:
Philosophers often make suggestions like the following: truth consists in correspondence to the facts; truth consists in coherence with a set of beliefs or propositions; truth is the ideal outcome of rational inquiry. According to the deflationist, however, such suggestions are mistaken, and, moreover, they all share a common mistake. The common mistake is to assume that truth has a nature of the kind that philosophers might find out about and develop theories of. For the deflationist, truth has no nature beyond what is captured in ordinary claims such as that ‘snow is white’ is true just in case snow is white. Philosophers looking for the nature of truth are bound to be frustrated, the deflationist says, because they are looking for something that isn't there.
The deflationary theory has gone by many different names, including at least the following: the redundancy theory, the disappearance theory, the no-truth theory, the disquotational theory, and the minimalist theory. There is no terminological consensus about how to use these labels:
...the intuition that a certain sentence or proposition ‘corresponds to the facts’ is the intuition that the sentence or proposition is true because of a certain way the world is; that is, the truth of the proposition is explained by some contingent fact which is usually external to the proposition itself. We might express this by saying that someone who endorses the correspondence intuition so understood would endorse:
The proposition that snow is white is true because snow is white
In particular, the deflationist does not have to say that someone who says ‘the proposition that snow is white corresponds to the facts’ is speaking falsely. Deflationists would do better to say that such a person is simply using a picturesque or ornate way of saying that the proposition is true...
So deflationism as a kind of nominalism rejects the ontic commitment of any truth value as a substantive property of any statement and truth is simply deflated away becoming non-existent. Under the POV of some deflationists holding skepticism of truth knowability, if one speaks of any corresponding facts one may act falsely according to their definition of truth. It's similar to Fitch's paradox which doubts that every truth is knowable in principle, so these deflationists may reject the validity or even existence of any correspondence or isomorphism as an adequate cause of some proposition's truth value since it may involve circular reasoning if no one can really know facts in an entirely objective way, ...