Why doesn't a "failed or expired authorization" for a Source trigger a Webhook event?

Hi,

Recently tried playing around the GCash / Grabpay integrations. An authorized payment does indeed trigger a webhook call.

However, it seems that whenever I tried to "fail" or to "expire" a Source, it doesn't trigger a webhook call.

Is this by design? If so, would you be able to suggest a flow on how we would mark an order as something like "abandoned" or "payment failed"?

Thanks,
John