Laravel Cashier generic trial not creating trial in Stripe dashboard

The Laravel Cashier docs show this code to create a "generic trial" (not attached to a subscription):

$user = User::create([
    // Populate other user properties...
    'trial_ends_at' => now()->addDays(10),
]);

After a registration endpoint is hit that creates a user and sets the trial_ends_at date to some time in the future, $user->onTrial() will return true, but in the Stripe dashboard, no trials are shown. It looks like this also causes webhooks not to fire when expected. Is there anything missing from this code snippet to let Stripe "know" about the new subscription?

How does Laravel notify Stripe that the user was created with a (generic) trial? That doesn't seem to be happening.