`DateInterval` no longer respects start/end class types

DateInterval iterated types no longer mirror parameter types

<?php
class TestClass extends DateTimeImmutable {}

$interval = new DatePeriod(
    new TestClass(),
    new DateInterval('P1D'),
    new TestClass('+5 days'),
);

var_dump(
    $interval->start, // TestClass
    $interval->end, // TestClass
);

foreach ($interval as $date) {
    var_dump($date); // TestClass in PHP 7.4-, DateTimeImmutable in PHP 8.0+
}

https://3v4l.org/VIQbo#v7.4.33 // TestClass
https://3v4l.org/VIQbo#v8.0.30 // DateTimeImmutable

This used to be consistent in PHP7.4 and below, start, end AND iterated values were all of the same class,
but since PHP 8.0, they are no longer consistent for some reason, and it's weird, because there should be no issue with compatibility having it the way it used to be. It used to be objectively better.

I only noticed it now because I had to update a legacy project from 7.3 to 8.3. Now I will also have to manually wrap any code that iterates over DatePeriod.

PHP Version

PHP 8.0+

Operating System

No response