At first I thought nice to know, but that won't help most people.
Then I went to check it out and found that I don't remember opening it since it's pretty much useless. It does show how much memory each consume and the _current_ energy impact. Utterly meaningless and doesn't help me at all to understand that a certain extension slows my browsing experience.
There’s a real discoverability issue with those kind of pages. They should be listed somewhere in some submenu. You can’t expect people to go through all the documentation like they used to go through manuals in decades past.
Chrome has chrome://chromeurls and Firefox has about:about (Firefox chrome urls tend to be actual browser resources, not information or settings or debugging. Eg with xul you used to be able to open the toolbars/browser ui itself in a window)
