Sure, but the providers for some of the biggest platforms are maintained by HashiCorp[1] - like the AWS, Azure, GCP, and Kubernetes providers[2], and it appears the Pulumi AWS provider (for example) _does_ use the Terraform AWS provider, even to this day[3].

1. https://developer.hashicorp.com/terraform/registry/providers... - "official" providers are maintained by HashiCorp

2. https://registry.terraform.io/browse/providers?tier=official - The filtered list of "official" providers maintained by HashiCorp

3. https://github.com/pulumi/pulumi-aws/tree/008c4360bc9fc24303... - Just prove it to myself, I can see the `upstream` git submodule, which embeds pulumi/terraform-provider-aws, which is a fork of hashicorp/terraform-provider-aws, although the repo was not created as a fork in Github, so it is not marked as a "fork" and so I have to compare commit histories to tell that it is a fork.