Not just migrations are hard, either; Google Cloud has put (almost?) zero effort into making it easy to use Cloud from systems running on Borg.

My old team was building a system that was half-GCP and half-Borg, and we had to write our own (extremely bad) Cloud Spanner fake for use in tests. In contrast, Infra Spanner is extremely well supported for tests. Same with BigQuery vs Dremel and many other systems.