I think the author is fighting the wrong problem. Webhooks are a notification mechanism first of all, not a data transfer protocol. You can view it as a control

I think the author is fighting the wrong problem. Webhooks are a notification mechanism first of all, not a data transfer protocol. You can view it as a control plane which can be mixed or not with a data plane. What they offer is a data plane and it makes sense. Although, it doesn't contradict the idea of webhooks, but rather complements it. A consumer can get notified via a webhook when new data is available. Whether the data itself comes with the webhook, or is available via an additional API request, is a matter of design. Personally, I like the idea of separating the control plane from the data plane. However, in some cases it can be an overkill.