There is probably a fair bit of electrical installation that still needs to occur. Then, commissioning will begin which could take some time. It’s a unique lift hill with a ton of motors that need to function in sync and be fine tuned. Additionally, the ride is going to have a brand new train design that has never been used before. It’s certainly not something you want to rush if you can help it. And after commissioning, the crew needs to be trained.According to the blog, the track circuit is complete. Don't know if that means all track work or what but June 23rd seems really far out if all track work is complete.
Plus, the June 23rd date is just the rededication ceremony for the park. Unless I’ve missed a detail, that doesn’t necessarily mean that it’s the opening day for ZZ.