Incoming webhook with no username/picture override does not show its creator's username/picture

A message from an incoming webhook with no username and picture override shows “webhook” as the username instead of the creator’s username and a default image instead of the creator’s profile picture.

Steps to reproduce
We’re using Server 6.1.0.

  1. The server needs to have username and profile picture overrides enabled.
  2. Create an incoming webhook, leave the fields for username and picture blank
  3. Post a message to the webhook. Don’t specify a username or picture.
  4. The message will appear as “webhook” with a default image.

Expected behavior
Leaving the username or profile picture blank should fallback to the creator’s name/picture. Then it would behave the same as when the override-settings are not enabled.
Otherwise that feature should not be called “override” as it actually changes the default behaviour of all webhooks. The expected behaviour is also documented here: Incoming Webhooks).

Overrides the username the message posts as.
Defaults to the username set during webhook creation or the webhook creator’s username if the former was not set.

Overrides the profile picture the message posts with.
Defaults to the URL set during webhook creation or the webhook creator’s profile picture if the former was not set.

Observed behavior
Messages sent to incoming webhooks with no overrides for username or profile picture are using “webhook” as the username and show a default picture.

Are we doing something wrong or is this a bug in Mattermost?