See https://moodle.org/mod/forum/discuss.php?d=434214

Basically, MDL-49609 made the contentitem workflow rely on the mod/lti:addcoursetool capability check. However, using content selection for an existing tool isn't the same thing as adding a course-level tool definition - and this results in the following:

Users who are able to USE tools in a course (but not CREATE them) are unable to use the content selection flow for those tools they have access to use.

There should be no reason these users, who have access to the tool, can't use deep linking.

This also prevents users properly controlling access to the creation of course-level tools because doing so will impact uses of tools the users do have access to.