If some cars do it and some cars don't on the same exact calibration in the same conditions, than the cause is likely mechanical variances between the two cars.
Example, maybe one car makes a little more boost than the other, so it calculates a higher torque value which then causes it to be noticeably more aggressive with tq mgmt.
Or, differing clutch clearances causing one trans to take longer to complete the 1-2 shift and so it does a boost/ignition and/or fuel cut to protect itself as it approaches the rpm limits. Both cars would have started the shift process at the same time with identical tunes but one car would complete the shift earlier while the other completes it later. Too much later and it'll feel like a momentary throttle chop.