Opcache is generating different observer output

Description

The following code:

--TEST--
Observer: Basic observability of userland methods
--EXTENSIONS--
zend_test
--INI--
zend_test.observer.enabled=1
zend_test.observer.observe_all=1
--FILE--
<?php
class TestClass
{
    private function bar()
    {
        echo 'Bar' . PHP_EOL;
        var_dump(array_reduce([1, 2, 3], fn ($a, $b) => $a + $b));
    }

    public function foo()
    {
        echo 'Foo' . PHP_EOL;
        $this->bar();
    }
}

$test = new TestClass();
$test->foo();
$test->foo();
$test->foo();

echo 'DONE' . PHP_EOL;
?>

Resulted in this output:
<!-- init TestClass::{closure}() --> shown 3x

But I expected this output instead:
<!-- init TestClass::{closure}() --> shown only once (as when run without opcache)

CI: https://github.com/php/php-src/actions/runs/4332385117/jobs/7564838868#step:10:156

/cc @dstogov

PHP Version

master with opcache

Operating System

any

Start by running the provided observer test case with opcache enabled and compare its output with a run without opcache. Investigate why the closure initialization message appears three times instead of once; done means the opcache run matches the expected observer output.