This stems from a bug report I made and the ensuing discussion with Michael Natterer, who told me to ask the question here.

See https://bugzilla.gnome.org/show_bug.cgi?id=723435

First, all the Layer/Transform entries also apply to the active channel, so putting that in the "Layer" menu is a bit misleading. But OK, we can live with that... but digging deeper:

The Flip/Rotate menu entries apply to the full drawable whether there is a selection or not. So these are not mere calls to the Flip tool. The offset transform also applies to the full drawable.

On the other hand, the "Arbitrary Rotation" that rotates layer or selection is not restricted to the layer. It isn't really essential since it does exactly the same thing as the Rotate tool. Or, if it's there on purpose, why are the other Transform tools excluded? And what will this entry become when we get the Universal Transform tool?

And while we are at it, "Layer/Scale layer" is also technically a transform and also only applies to the drawable and not to the selection, so it would make sense in Layer/Transform, at least much more sense than the arbitrary rotation.

I looked into this because this organization was very confusing for a new user.

What do you think?