Gimp 2.2.10 on Windows.
F1 launched browser into help docs.
/crop - took me to the link.
Click went to the crop tool description.

I'm a bit confused by what you meant by the menu item though.

I only see "Autocrop Image" and "Zealous Crop" on the menu.

I've used "Autocrop" to remove whitespace that surrounded images.

As others have point out, using Gimp or Photoshop to create the type of images that are on that site a "non-trivial", and this is a major understatement. Fscking hard is where it begins.