Truly anonymous data is not subject to the GDPR. So the question is whether the data they are collecting is truly anonymous. They seem to be claiming or suggesting "Yes it is" https://code.visualstudio.com/docs/getstarted/telemetry#_gdp... .
> MacAddressHash - Used to identify a user of VS Code. This is hashed once on the client side and then hashed again on the pipeline side to make it impossible to identify a given user. On VS Code for the Web, a UUID is generated for this case.
A hash of a hash is about as expansive as a hash and it still uniquely identifies a machine, tying telemetry events to a specific user's machine. Microsoft's own telemetry description generator calls the field "EndUserPseudonymizedInformation". Pseudonymisation is inherently not anonymisation.
This bullshit is why I keep my PiHole on for my dev environment.