Data races are a specific race condition - they may be safe or cause tearing.

Serially, completely synchronously overwriting values is none of these categories though.

You're mixing up quite a few somewhat related but different concepts: data races, race conditions, concurrency and parallelism.

Concurrency is needed for race conditions, parallelism is needed for data races. Many single threaded runtimes including JS have concurrency, and hence the potential for race conditions, but don't have parallelism and hence no data races.