We currently run on Azure. GitLab integrates deeply with Kubernetes and specifically GKE, so it makes sense to run GitLab.com there: https://about.gitlab.com/2018/04/05/gke-gitlab-integration/
Isn't Netflix running on the same platform (AWS) as Amazon Prime?
Realistic speaking, what's the huge win for GitLab?
All it takes a someone in the billing department leaking metadata to a project manager for confidential information to leak (traffic numbers, storage trends etc.).
Sure trust every employee of your only real competitor if you want, but I wouldn't if it was my business and I had alternatives.