Sam, welcome to the forum.
First, a bit of house keeping. I'll move this thread to the "Rigging" section, because it's equally applicable to all types of DaySailer, and of general interest.
The wiring always serves the purpose of keeping the shroud attached to the spreader, but it can also serve the purpose of fixing the location of the spreader on the shroud. If your spreaders are the kind that have an extra-beefy bracket that firmly holds the spreader horizontal, I would allow some play. Otherwise,the spreader, if placed where it should be when the shrouds are tight, would be under some tension when the shrouds are slack, and the upper portion between the tang on the mast ("hounds") and the spreader in no longer stretched.
However, if you have the old-style spreader brackets that are simply a pin through the spreader tube, and which allow a bit of wiggle around the horizontal position, I would recommend locking the spreader end in place. That style of spreader is easily damaged if you catch it on anything while the mast is in storage or being raised. Fixing it to the shroud means any push downward is resisted by the shroud (and as long as you cinch the lower ends of the shrouds to the mast, there's some protection in the other direction as well).
After breaking the same spreader twice (!) within a week, I changed that one so the place where it attaches to the mast is
jury-rigged in a way that allows it to swing up and down 10-15°. However, it is firmly wired in place, using a technique different from the one shown on the video. First, it seems to me that the wire I used was stiffer. I started out as shown, but wrapped each end firmly around the shroud (using pliers) five or six times, clipped the end, and using pliers made the end lie flush with the last winding.
Whichever technique you use, make sure to wrap the connection in self-amalgamating (rigger's) tape, unless you have a rubber or plastic spreader boot. Your sails will thank you.
On my boat, the wiring is just tight enough to firmly hold the spreader, but can be adjusted (after the main has been raised) with a vigorous shove from below with a paddle (pushing at the spreader directly where it meets the shroud). The last time some adjustment was necessary was over 20 trips ago. . . .