Debug messages refer to /wp-includes/functions.php

I'm having an issue where debug messages refer to lines of code in /wp-includes/functions.php instead of the lines in the child-theme or plugin actually causing the issue.

The lines referred to (most often) appear to simply be the logic that generates the error messages for deprecated code: /wp-includes/functions.php on line 5316

Is this just the way that deprecated code errors work or have I stepped on my own foot with a setting somewhere non-obvious? I triggered an undefined function error as a test and it told me exactly where it was, as I would normally expect.