topology.generate() continues running after job is closed (until JVM exits)

I noticed this in a test environment but expect it happens in a normal environment as well. I'll attach a simple test that demonstrates the problem.

The test's Supplier.get() is: "sleep(1sec); print and return next value"
It runs the job for 5sec then closes it and sleeps for another 10sec before
exiting.

Here's its output:
generated 1
generated 2
generated 3
generated 4
generated 5
generated 6
Job current state: CLOSED
sleeping... it's a bug if still generating tuples
generated 7
generated 8
generated 9
generated 10
generated 11
generated 12
generated 13
generated 14
generated 15
done