Wider first components have higher fitted DM on 70 of 84 paired days for FRB20220912A in CHIME Catalog 2

We compare the widest and narrowest first burst components from the same source on the same day in CHIME/FRB Catalog 2, release 20251231. FRB20220912A has a larger fitted dispersion measure for the wider event on 70 of 84 paired days. The mean difference is 2.136 pc cm^-3, with a nominal day-resample interval of 1.630 to 2.677. Signal-to-noise, component-count, and peak-frequency cuts keep positive intervals. An early width model lowers later squared error by 31 percent against the early mean, but the error-gain interval includes zero. Three sources pass the five-day rule; the other two have inconclusive corrected swap tests. Prior work already reports morphology bias in this source. We add a same-day catalog test, not a new plasma event. Shared fit errors, selection, rapid plasma effects, and missing raw-spectrum tests limit physical claims. Code, accepted events, all pairs, hashes, figures, controls, and offline instructions are included.

astronomy · CHIME · fast radio bursts · dispersion measure · burst width · same-day pairs · FRB20220912A