Ada's tasks don't require an explicit join, they're lexically scoped. So if you have a procedure with two subtasks that procedure will not terminate until those two subtasks have terminated (by whatever means they may be terminated, running to completion or an explicit `abort SomeTask;`).

Here are a couple pages on Tasking in Ada:

https://learn.adacore.com/courses/intro-to-ada/chapters/task... - doesn't compare to any other languages, just Ada code.

https://learn.adacore.com/courses/Ada_For_The_CPP_Java_Devel... - Includes comparisons to Java and C++.

http://www.ada-auth.org/standards/22rm/html/RM-9-8.html - more on cancellation via the abort statement. If you abort a task with subtasks running, it will terminate all of them.

Ada has some escape hatches around its task system that "breaks" from structured concurrency, but pretty much everything people have been asking for around structured concurrency is already in Ada and mostly the default behavior.