Yes that’s because curl doesn’t inherit keychain/macOS trust settings. That’s a separate tool with its own thang going on. You can have it trust your custom cert, google it, might be a headache.
You can temporarily disable cert verification but no clue what the option is for wp_safe_remote_get().
For example in file_get_content() you can pass a $context which is essentially curl options, one of them being ‘verify_peer’ => false.
$options = array(
'ssl' => array(
'verify_peer' => false
)
);
$myOwnShit = file_get_contents($url, '', stream_context_create($options));
I’m facing a similar issue where on the same OS version localwp fails to point at /etc/ssl/cert.pem so no https requests can be verified.