I can see how the existing text is unclear. Having done a few tests on this myself it looks like init.d services that are not executable are not added (or are even removed) when update-rc.d is run with the "enable" parameter. When update-rc.d is run with "disable" a link is set up for disabling scripts as expected, but the script might not run properly.
I'm going to make a slight change to the suggested wording and commit it. So let's consider this fixed upstream. Can probably close unless there are further suggestions on how to make the warning more clear. - Jesse
