The Open Compute designs (which is where this will end up) aren't just a list of parts. They include things like blueprints for custom chassis, circuit boards for power supplies and even designs for solid state storage devices[1][2][3]. The also include the source code for custom management software[4].
While it is true that they don't generally design their own logic boards, it is quite a long way from a list of parts.
I don't think backblaze called their case designs open source hardware.
You'd be wrong about that: This new Storage Pod performs four times faster, is simpler to assemble, and delivers our lowest cost per gigabyte of data storage yet. And, once again, it’s open source.[5]
I think "open source" is completely appropriate here, and to be honest I don't quite understand your objection.
[1] http://www.opencompute.org/wiki/Server/SpecsAndDesigns
[2] http://www.opencompute.org/projects/chassis/
[3] http://www.opencompute.org/projects/power-supply/
[4] http://www.opencompute.org/projects/hardware-management/