This is just the first stage of the work that has to be done. Transforming a shop of very minimal layout into a very complex restuarant is not easy by any means, this picture above really only shows the track. They could still have the system that runs it all to install, electrics to wire, kitchens, fridges,freezers to install, diving walls to build. Not to mention decorating it, testing it all out then the important stage of training the staff to manage it all!
One thing is for sure Merlin will not want to lose out on money this season so they will want it open ASAP. They may also just be playing it safe, don't want to book tables and it not open....just more headlines! However if it opens ahead of schedule positivity flows