By the looks of Thorpe's updates this winter, it seems as though Rush had a LOT of work done to it this closed season, like it does every 3-4 seasons. When this happens, it usually opens late (last time it happened it opened April-time I believe?). So to be opening a day late is pretty good going. Seemingly the time it takes for that amount of maintenance to occur is just a bit longer than the time they have during closed season.
Given that Thorpe have posted videos of Swarm testing, and it has been the most reliable major attraction at Thorpe the past 4 seasons, obviously something unexpected has cropped up for it's slightly late opening.
Obviously rides opening late is a bad thing, and given that things like this have happened before, it could be an indication that they need more budget for maintenance, or they need a longer closed season. But given what we, as enthusiasts, know, I'm not going to hold the slightly delayed opening of Rush and Swarm against them.