--output has no effect

[rhuss]

⛵ kind-knative Documents/Talks/wjax-knative-2024/demo
10:54 ✗ kn event send -o yaml --to demo -f message=Hello
📬 Sending event within the cluster Done
3582 INFO Event (ID: 9a07dbd5-5767-4368-a611-34649527b076) have been sent.

⛵ kind-knative Documents/Talks/wjax-knative-2024/demo
10:54 ➜ kn event send -o human --to demo -f message=Hello
📬 Sending event within the cluster Done
4093 INFO Event (ID: a5ba200e-fa68-4a1b-a630-3512c88c31ea) have been sent.

⛵ kind-knative Documents/Talks/wjax-knative-2024/demo
10:55 ➜ kn event send -o json --to demo -f message=Hello
📬 Sending event within the cluster Done
3901 INFO Event (ID: 0ea7a3d4-09d1-42e1-9d02-1a6b95fb0e4b) have been sent.

What is --output supposed to do ?
(minor nit: It's "Event .... has been sent", not "Event ... have been sent")