If you cut both sides you end up with very short bushings..
Maybe I'm just tired from flying all over the place (just checked into my 2nd hotel in two cities in two days at 1AM and am flying back out tomorrow after meetings first thing). The bushings wouldn't be impacted by shortening the ends of the tube, they'd just get pressed in after. This actually has needle bearings regardless.
Now that I look at the photos, it actually looks like the entire swingarm was cut right down the middle, channeled and put back together. The big square tube is also cut right down the middle.
So it appears the swingarm was narrowed and shock mounts added to all match up with the XS650 frame. Lots of effort put into it. Maybe someone on eBay would appreciate it a lot
It would seem a beefy swingarm like this is well above and beyond the rest of the chassis.