I agree with @somethingsomething as based on this documentation, gsutil commands are not listed here. Although it was not mentioned that gsutil is not allowed nor does it work to ignore files included in the .gcloudignore file, it seems like .gcloudignore only works when deploying an app or function.

I tried replicating your issue and I got the same results as yours. The files included in .gcloudignore files are still pushed to the bucket using gsutil rsync command. Upon adding the -x command, the files are also not pushed to the bucket.

On the other hand, I also tried deploying a function using gcloud functions deploy. It worked well and ignored the files I included in the .gcloudignore file.