It’s still an accurate term under that definition. Single-tenant cloud is technically multi-tenant with respect to the underlying cloud provider (AWS/GCP/etc.),

It’s still an accurate term under that definition. Single-tenant cloud is technically multi-tenant with respect to the underlying cloud provider (AWS/GCP/etc.), but not with respect to the software service provider (GitLab in this case). But I believe language and communication are emergent, decentralized phenomena. Single-tenant cloud is a good and useful term.