Sorry if this is a question with a really obvious answer. I'm pretty new to working on bikes (this year) but think I can usually see what's going on, with a little help from Lennard Zinn. This has me stumped though.

We have a beat up '96 Specialized Hardrock which my 13 y o son and I are using as a demo/project. We're going to SS it, give it a rattle can paint job, etc. We cannibalized the brakes to get a working set of brakes (Shimano Altus with the funky plastic part) for another Hardrock which we sold. So I was looking for some inexpensive canti brakes for this bike, and grabbed a set of NOS Suntour XS from eBay. I figured at $6 + shipping I couldn't go far wrong.

But now I don't get it: how is this (the left) supposed to work? The instructions note the 'spring tension balancing sleeve nut' but the spring doesn't come through it, so how does it secure to the boss? The other side is normal, with the spring end poking out with plenty of room to insert into the boss hole. I checked and this is not because the springs got switched, they're both the same.

I did try installing the brakes in case there was some magic I just didn't understand but it went as I expected: completely loose, then completely tight, with no spring tension because the spring isn't engaged.

Am I missing something here? And if so, is it an actual part or something in my head? Thanks for any advice.
(dang it...I put a pic in but forgot to upload it...sorry--here it is!)