1. HashiCorp Terraform Documentation, "State Locking": This document explicitly states that locking is not a universal feature. "Not all backends support locking. The documentation for each backend includes details about whether it supports locking." This directly refutes the first part of the question.
Source: HashiCorp, Terraform Documentation, Language, State, "State Locking".
Reference: developer.hashicorp.com/terraform/language/state/locking
2. HashiCorp Terraform Documentation, "Backend Type: local": The documentation for the standard local backend makes no mention of locking capabilities, as it is intended for individual use where concurrent operations are not a concern. This serves as a specific example of a standard backend without locking.
Source: HashiCorp, Terraform Documentation, Language, Settings, Backends, "Standard Backends: local".
Reference: developer.hashicorp.com/terraform/language/settings/backends/local
3. HashiCorp Terraform Documentation, "Backend Type: remote": This page details the functionality of the remote backend, which is designed for Terraform Cloud and Enterprise. It describes remote operations as a key feature: "The remote backend can also be configured to execute Terraform operations in a remote environment..." This highlights that remote execution is a specific feature of this backend, not a general feature of all backends.
Source: HashiCorp, Terraform Documentation, Language, Settings, Backends, "Standard Backends: remote".
Reference: developer.hashicorp.com/terraform/language/settings/backends/remote
4. HashiCorp Terraform Documentation, "Backend Type: s3": The documentation for the s3 backend shows that it supports locking via a DynamoDB table, but it does not perform remote operations. The plan and apply commands are executed locally, accessing the state file stored remotely in the S3 bucket. This distinguishes remote state storage from remote operations.
Source: HashiCorp, Terraform Documentation, Language, Settings, Backends, "Standard Backends: s3".
Reference: developer.hashicorp.com/terraform/language/settings/backends/s3 (See section on "State Locking and Consistency").