Error level mapping not works as expected

[pro2s]

I added a log level mapping for deprecate error level, but deprecated errors pass to logger.
We use the Datadog logger.

How I can see mapping works correctly on wp-content/plugins/decalog/includes/listeners/class-phplistener.php
But there is wp-content/fatal-error-handler.php (installed from wp-content/plugins/decalog/assets/fatal-error-handler.php) and this handler keep levels as is and logs pass to the datadog logs.

Is this a bug or can this behavior be changed?