Subtests order/format change as of v4.3

[beatngu13]

I think I'm facing an issue that might be related to #56. With v4.2.1, TapProducer#dump(TestSet) resulted in something like:

1..2
ok 1 Some test case 0
    1..3
    ok 1 Some action
    ok 2 Some action
    ok 3 Some action
ok 2 Some test case 1
    1..3
    ok 1 Some action
    ok 2 Some action
    ok 3 Some action

Whereas as of v4.3, the result is:

1..2
    1..3
    ok 1 Some action
    ok 2 Some action
    ok 3 Some action
ok 1 Some test case 0
    1..3
    ok 1 Some action
    ok 2 Some action
    ok 3 Some action
ok 2 Some test case 1

It looks like this is caused by a34d494 as this change is also reflected in the test class TestIssue3504508.

I'm not that familiar with TAP in general, but I assume this is somewhat related to TestAnything/Specification#2?

I just wonder which order/format is "correct"?