Missing trait is E_ERROR but missing extends/implements is Exception when autoloaded?

[kkmuffme]

Description

The following code:

<?php
spl_autoload_register( function ( $class_name ) { 
    if ( $class_name === 'Foo' ) {
        require __DIR__ . '/foo.php';
    }
} );
try {
    class_exists( Foo::class );
} catch ( Throwable $e ) {
    echo 'catch' . PHP_EOL;
}

foo.php

class Foo {
    use Bar;
}

Resulted in this output:

Trait "Bar" not found

But I expected this output instead:

catch

Change foo.php to

class Foo extends Bar {}

and you will get the expected output. It's not consistent/illogical that traits behave differently in this regard?

PHP Version

PHP 8.5

Operating System

No response