FPM: error_log entries all on same line

Description

The following code:

<?php
echo 'try err msg on line 1<p>';
error_log("err on line 1");
echo 'try err msg on line 2<p>';
error_log('err on line 2');
echo 'try err msg on line 3<p>';
error_log('err on line 3');
?>

Resulted in this output:

[Mon Mar 20 15:07:40.253904 2023] [proxy_fcgi:error] [pid 122391:tid 140026615572224] [client 129.71.34.33:53261] AH01071: Got error 'PHP message: err on line 1PHP message: err on line 2PHP message: err on line 3'

But I expected something similar to this instead:

[Mon Mar 20 13:25:38.221700 2023] [fcgid:warn] [pid 97183:tid 140026511869696] [client 129.71.34.33:57883] mod_fcgid: stderr: err on line 1
[Mon Mar 20 13:25:38.221753 2023] [fcgid:warn] [pid 97183:tid 140026511869696] [client 129.71.34.33:57883] mod_fcgid: stderr: err on line 2
[Mon Mar 20 13:25:38.221762 2023] [fcgid:warn] [pid 97183:tid 140026511869696] [client 129.71.34.33:57883] mod_fcgid: stderr: err on line 3

If I change back to FCGId I do get the above three individual log entries -- in fact my example above, as you can see, is from FCGId.

Either I am missing a setting in my PHP and/or FPM config (some flush or cache setting?) or FPM is the culprit here :-) If I send three different distinct error messages, each should be standalone and not concatenated together -- again FCGId logs things properly.

PHP Version

PHP 8.2.4

Operating System

No response