If you mean that MetricKit on iOS 27 is better about including terminationReason, I'll watch for that. I do also plan to support the new MetricKit.
As for the Xcode organizer, its top entry in Crashes under Reports does look like a 0xdead10cc termination - it carries that code if I go look at the raw report on disk (side note - the Organizer does not expose these terminations well - FB12292887). But on the Terminations screen under Metrics, it shows background terminations as being 98% System Pressure, and 1% File Lock and 1% Other. I don't believe 1% of terminations works out to enough to explain the numbers of reports I've been seeing, and certainly not to the count shown on that top entry in Crashes under Reports.
As another signal, the original impetus for me chasing this is that the Crashes metric in App Store Connect for my app shows a higher crash count per day than I expect, not matching any other reporting source I have. It's why I started uploading all my MetricKit reports from devices in the field.