Pro tip: adjusting the alignment bolts is best done with a flare nut wrench (I figured out the name for this tool finally!); anyhow why even mess with the axle nut and adjusters at all for a belt swap...?
I'm not convinced on the use of a flare wrench.
I just tried using mine & it's too bulky to engage the nut/bolt.
These (bolt & nut) shouldn't be over thightened as all they do is to create & hold the proper belt tension until the axle nut is torqued down so a simple open wrench should be sufficient in thightening/loosing.
As to why to loosen the axle & tension jack bolts?
For ease of installation. I'm not convinced it can be done without loosening them.
Be careful spinning on a belt as you don't want to force it on & put undue stress on the wheel/motor bearings.
I think it's highly unlikely that a new belt will be happy in the exact position (jack bolts) of the old belt (at least the 14mm with its limited tension range).
I recommend removing the jack bolts (especially the left one as it does all the work) & grinding off the metal print on the heads because if not removed, it will dig into the soft aluminum of the swing axle. At the same time, coat the threads as well as heads with some anti seize.