nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpq0ae605fgpw08r8d2u7u65wu82n5n02gzv4wef797z5dk7g3w8smqz8zuq0 (nprofile…zuq0) the data he's using is actually the official frequency measurements, which I assume come from a relatively "clean" source:
https://www.neso.energy/data-portal/system-frequency-data
It's also only at 1Hz resolution so I suspect the artifacts it's picking up likely represent differences in balancing/frequency control rather than inverter noise.