actually you can test it via diawi.com but it's hilarious cause whole point of appstore connect it ability to test and submit the same build on the same platform and you can't have a lot of testers with diawi so it's only for small closed test groups

actually you can via diawi but it's pain in the аss and you can't have a lot of testers like that. whole point appstore connect is to provide easy and functuional service to test and submit the same builds. Now we need to test it in one place than submit on appstore