Physical theories often go beyond just predictions, and attempt to specify a correspondence between a formalism and physical reality.

Quarks are an example. Quarks were conceptualized as a mathematical simplification, and only later were recognized as real physical things - or at least as real as protons.

In QM we have physical quantities (an electron's mass) and unphysical quantities (an electron's phase). But there's open questions, like the wavefunction - can that be placed in correspondence with reality? We don't really know. This is the "ontic" vs "epistemic" debate.