Aristotle: I think you're mostly right. After doing much more investigation, I think it may have been an unintentional screw up by example.com. Their site is obviously code generated, but it is as far as I can tell, legit and does a lot of selling through A--. They also normally have a couple links to us on one page. I think what happened is they were experimenting with a new website building algo and/or mass 301 redirects and instead of linking to A-- linked them ALL to us and possibly others (what are the odds?). They managed to get 280K crawled in an awful short time before realizing the error.
An e-mail to example.com through their only form of contact (an onsite form) resulted in an error, so I'm not sure I got through. Domain Reg is private.
I'm just keeping my fingers crossed and waiting for the message from G about bogus backlinks, with my finger on the disavow link.