Intl MessageFormatter using incorrect timezone

Description

The following code:

<?php
\Locale::setDefault('en-CA');
date_default_timezone_set('America/Edmonton');

$now = new \DateTime();

echo "DateFormatter - [" . \IntlDateFormatter::formatObject($now, [\IntlDateFormatter::FULL, \IntlDateFormatter::FULL]) . "]\n";

echo "Singular - [" . \MessageFormatter::formatMessage(
  \Locale::getDefault(),
  '{0, date, full} - {0, time, full}',
  [$now]
) . "]\n";

echo "Plural - [" . \MessageFormatter::formatMessage(
  \Locale::getDefault(),
  '{0, plural, 
        =0    {{1, date, full} - {1, time, full}.}
        other {{1, date, full} - {1, time, full}}
   }',
  [1, $now]
) . "]\n";
?>

Resulted in this output:
DateFormatter - [Friday, March 4, 2022 at 1:28:49 p.m. Mountain Standard Time]
Singular - [Friday, March 4, 2022 - 1:28:49 p.m. Mountain Standard Time]
Plural - [Friday, March 4, 2022 - 8:28:49 p.m. Coordinated Universal Time]

But I expected this output instead:
Plural ICU format to MessageFormatter should return the same as that shown by Singular but it seems to be ignoring the default timezone set using date_default_timezone_set() and defaulting to server timezone of UTC when using the Plural form of ICU.

PHP Version

PHP 8.1.3

Operating System

Ubuntu 18.04.6 LTS

No documentation file or test is named. Start by reproducing the supplied PHP 8.1.3 example, comparing IntlDateFormatter, singular MessageFormatter, and plural MessageFormatter output after date_default_timezone_set('America/Edmonton'); done means establishing whether the behavior needs documentation or should be reported to the PHP implementation.