It could have been in relation to that, but I don't specifically remember anything about that system that would have needed a part like this, (in fact, if you look at the first photo in the linked article, you can see just about the only PCB in the whole system is the motherboard.) since it's basically a totally standard ATX or BTX motherboard in a modified Power Mac G5 case.
But, Apple's entire product line was under development, so it could have been anything -- a RAID card for the Xserve, a drive backplane for the Mac Pro, a Mac mini motherboard, or the beginnings of some kind of internal testing rig akin to the TechStep.