They started tearing out the track on the back half in September. So over 4 months ago. I haven't seen anyone post any info on when they started repouring those footers. From Nearmap, we can tell they were still busting out the old ones on November 14th. They still are pouring ones on the front half. It's hard to say what the pour schedule was like on the back half. So if they started pouring in late November, they could be on a 60 day cure. Maybe as little as 30, but that gets into engineering. Hanging track takes less time than it would to redo a footer the way they did it. Or for that matter, less time than it would take to build and paint a piece of track. The hanging track is the easy part of all of this. The footer crew would take more time to do their job than the erection crew in areas they don't have to deal with guests, so a staggered curing time is possible.
If I was going to put a solid guess though, I'd say they only had so much track on site, got a crane rented to hang it, let the crane go back, and are going to wait till they have a yard full of track again to get the crane back for a few days. Most of the time they schedule coaster construction so they don't get a crane on site till they know they can do the whole job before the crane goes back. More economical, but you have to wait till all of your ducks are in a row to start. Meaning that the completion day gets pushed back. By doing it this way, they can get done quicker at a little more crane/erection crew cost.
If I was going to put a solid guess though, I'd say they only had so much track on site, got a crane rented to hang it, let the crane go back, and are going to wait till they have a yard full of track again to get the crane back for a few days. Most of the time they schedule coaster construction so they don't get a crane on site till they know they can do the whole job before the crane goes back. More economical, but you have to wait till all of your ducks are in a row to start. Meaning that the completion day gets pushed back. By doing it this way, they can get done quicker at a little more crane/erection crew cost.