EDIT: I should have mentioned, although the power output from the Kickr Core is unsmoothed, I’ve smoothed the output of both power sources myself in the plot.
It’s common to see strain gauge based power meter output appear to be much noisier versus a smart trainer output. Trainers typically calculate power based on the speed of the flywheel, that will naturally smooth out the readings.
Example of Pettit, first one recorded from my Neo 2T and the 2nd from a Stages: