I remember a factory EPA type sticker on a 1989 C-series fire truck engine (Cat 3208)
This engine does not meet [x] spec but it’s OK because the fines have been paid.
2006-ish Cummins 8.3 liter engines had high pressure common rail and catalyst, but no EGR, they used credits from the larger 15-ish liter engines to keep the smaller ones more simple.
Remember the Ford ambulances with the same old 6.0 diesel in the van chassis, long after everything else had gone to the DPF 6.4 or whatever?
No new thing under the sun. Always cutting and sewing the blanket.