I am observing the same behaivior. When you have 2 order status you can not customize the emails for both of them.
Only one will take the changes when you customize the email and the other will replicate these changes and ignore the changes you make.
The preview works in the sense that it shows the emails, but the behaivior that i am describing is replicated in the preview, so if you change the subject for status 2, in the preview you will see the subject of status 1 and this will be what you are finally sending as an email not what the customization for status 2 should be…
