Code sample:

<?php

class User
{
public int $id;
public string $name;
}

$reflection = new ReflectionClass(User::class);
$user = $reflection->newLazyGhost(function (User $user): void {
throw new \RuntimeException('Initialization should not be called');
});

var_dump($reflection->isUninitializedLazyObject($user));

When running this script, the output is "true".
But when a breakpoint is added on the var_dump line, the initialization closure is called.