Is there really no way to see all watch tower issues in one place in the iOS app?
At present, with 1Password 7 for iOS, that is correct. That is something we hope to improve in 1Password 8 for iOS. It is currently possible to view a per-vault Watchtower summary in the web app at https://start.1password.com/
Here is a peek at the overview report we have in 1Password 8 for Mac, currently in Early Access: