Using the JQL search API is the way to go to search out all issue for any user within your organization. Your JQL result depends on other permission or filter factors configured within those projects you're searching. Therefore, understanding what issues your user is able to search within your instance would be help you. Also, you still need to use the issue search endpoint to see the contents of the issue afterward.
so if my permissions allow to get any specific issue by requesting 'GET /rest/api/3/issue/{issueIdOrKey}' then why this request gives only a subset of all issues?
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
Again, the JQL results depends on other permissions! If you search through the UI, do you get the same result as the API? My guess is for you to evaluate if you have the permission to view all worklogs within your project and not just your own.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.