Redis – Is ProcessorCount is sensible value for maxCount in SemaphoreSlim?

In code of my colleagues I’ve noticed code like this:

private Task FetchAllKeysFromRedis(List<string> keys, ConcurrentBag<RedisModel> resultsBag, CancellationToken cancellationToken)
{
        var parallelism = Environment.ProcessorCount;
        var semafore = new SemaphoreSlim(initialCount: parallelism, maxCount: parallelism);
        var tasks = new List<Task>();
        foreach (var key in keys)
        {
            cancellationToken.ThrowIfCancellationRequested();
            tasks.Add(FetchFromRedis(key, semafore, resultsBag, cancellationToken));
        }

        return Task.WhenAll(tasks);

List<string> keys approximately contains around 1000 keys, and FetchFromRedis method asynchronously execute I/O operaion (fetch from Redis), so to sum up it executes around 1000 of I/O operations.

Critical section look like this:

private async Task FetchFromRedis(string key, SemaphoreSlim semafore, ConcurrentBag<RedisResult> resultsBag, CancellationToken cancellationToken)
{
     await semafore.WaitAsync(cancellationToken);
     try
     {
         var redisResult = await _getRedisResultFromRedis.ExecuteAsync(key, cancellationToken);
         if (redisResult != null)
              resultsBag.Add(redisResult);
      
         finally
         {
            semafore.Release();
         }
      }

My question: is Environment.ProcessorCount sensible maxCount for SemaphoreSlim? As it will limit count of threads that can step into critical section to very low, like 8, and time of execution will be much longer?

If it not sensible, then what is sensible value for maxCount of threads?

My opinion: since it involves IO, most of the time will just be waiting, no processor time needed. So limiting concurrency to the number of cores make little sense.