Because ImportFullyQualifiedNamesRector rector only checks files that have namespaced defined it it does not fix FQCNs in a procedural code like this.
<?php
function foo() {
$baz = \Foo\Bar::Baz;
}
-----
<?php
use Foo\Bar;
function foo() {
$baz = Bar::BAZ;
}
Because ImportFullyQualifiedNamesRector rector only checks files that have namespaced defined it it does not fix FQCNs in a procedural code like this.