You're absolutely right! Sorry to send you down a dead-end (but thanks for reporting it). It appears that native dialogs block the test thread. We'll have to do a bit of digging to see if/how we might support this.
In the meantime, are there any workarounds for your use case? That is, can you accomplish the same actions programmatically? I know this isn't totally satisfying but it might get you unblocked.
Thanks for submitting a feature request BTW. We'll look into it and be in touch.