i'm unable to replicate

Well, the instructions in the issue say that it might be hard to replicate.

Quote from the PHP manual:
microtime(bool $as_float = false): string|float

Emphasis on "time in seconds"! The value is rounded to seconds. This means that it is not incomprehensible if double values come out when a loop is run through faster if we use microtime(true)

When I test with a loop like this:

$withTrue = [];
$woTrue = [];

for ($i = 0; $i < 100000; $i++)
{
	$withTrue[] = microtime(true);
	//$woTrue[] = microtime();
}

echo '$withTrue: <pre>' . print_r($withTrue, true) . '</pre>';
// echo '$woTrue: <pre>' . print_r($woTrue, true) . '</pre>';

exit;

OR use a counted output: which outputs just two values that are never equal in my test cases:

echo 'count($withTrue): <pre>' . print_r(count($withTrue), true) . '</pre>';

$filter = array_unique($withTrue);

echo 'count($filter): <pre>' . print_r(count($filter), true) . '</pre>';
exit;

• $withTrue case: I need several thousand loops before I get the first different time value. With the last test I needed ~16.000 loops.
• $woTrue case: Also not reliable. Several blocks with several double time values. With just 100 loops => 75 double time values.