Post ProdigyI tried that unfortunately, it still doesn't work for me.
I have the same experience and steps as your video up to 51 seconds in.
At 1:11 in your video your App Workspace shows no icon and this happens to me with ALL my app workspaces which is odd.
I have several, some of the apps that have icons show the icons but none of them (even those with icons in the App page) show icons on the My Workspaces area.
At 1:20 the workspace in the video shows the app icon, but mine never refresh to show that.
Basically, it seems I never get past 1:11 in your video, the updated icon never leaves the workgroup and makes it into the Power BI side.
Here is what my O365 group page looks like, with several of them having images uploaded to the system and displaying:
They have the images in the O365 group, they just never sync back to Power BI