That's certainly true, but it does look like in this case. I did the preliminary benchmarking on an 8-thread CPU (the actual HPC cluster has higher counts), and

That's certainly true, but it does look like in this case. I did the preliminary benchmarking on an 8-thread CPU (the actual HPC cluster has higher counts), and the total execution time on the processing was just under 8x, which I imagine came from the OS-level thread management overhead. I still need to check that pattern holds once thread counts increases, but I'm fairly optimistic it'll work out as long as I don't run into thermal throttling or I/O limits.