(Some of) the devil is in the details. You might want to look at the announcement [1] and the support page [2]. It's only certain services (although it includes GCS and VM persistent disks), and it's really meant for a full migration out of GCP. So if you want to migrate only a portion of your data to create a multi-cloud setup, this might not work.
Still, it's great.
[1]: https://cloud.google.com/blog/products/networking/eliminatin...
[2]: https://cloud.google.com/exit-cloud