You're right in 90% of cases, since most of the official Pulumi providers are generated using the pulumi-tfgen bridge where it basically translates the TF providers to code ones. There are exceptions (like the Pulumi K8s provider) where the Pulumi Provider SDK is being used.

I don't see anything problematic in it, even better if we can use the stable, well-known stuff and re-use it. My point was mostly that Pulumi gives you the freedom of creating custom provision logic.