Bug Report

• Yes, I reviewed the contribution guidelines.
• Yes, more specifically, I reviewed the guidelines on how to write clear bug reports.

Describe the current, buggy behavior

In a object cache (object-cache.php) drop-in, any do_hook and 'when' are not executed.

function foo() {
    echo 'hello' . PHP_EOL;
}
WP_CLI::add_command( 'bar', 'foo', array( 'when' => 'run_this_early' ) );

WP_CLI::do_hook( 'run_this_early' );

Describe what you expect as the correct outcome

It should run the callback of the command where the do_hook is, but instead it won't but load the rest of WP

Let us know what environment you are running this on
WP CLI 2.12.0