You're right.
We've just tested it.
Well, the "selecting path" scenarios with OpenJDK are:
1) old dialog:
pain, but intuitive (the user wont get anything what looks like error / bug).
2)new dialog:
much less pain, but every user who isn't familiar with the issue wouldn't know what's happening (user would be lost, it might look like a bug). That's majority of existing users + all new users.
I think it's not worth it doing this.
If you could set the new one for Save/Open and the old one for setting images path - it would be the best for now, but I guess it's a global setting so that wouldn't be easy so thats not a good option.
So,
I would go for the old dialog in the OpenJDK.
Those who have Java will can work with the System Java version.
Those who haven't - will work in the OpenJDK plus they can still install Java and then use System Java.
They can find out here at forum, or maybe would be good to put this information to the change log / read me file / documentation, so it's easier to find.
Its more than good for now, maybe can be fixed in future. Now I guess you have more cool features to work on 🙂
Still - it's a huge improvement because now there is the option with the system java app 🙂