How can I query against a boolean when using LINQ in CosmosDB SDK v3.0 sync count queries?

I am using a synchronous pattern to count items held in CosmosDB, specifying a predicate and using GetItemLinqQueryable

This works nicely, counting all ReportRecord items with a specific field value:

 var count = _cosmosClient.GetContainer(DATABASE_ID, CONTAINER_ID)
                .GetItemLinqQueryable<ReportRecord>(true)
                .Count(r => r.Name.Equals("Smith"));

However, if I try to check a boolean is true in the predicate it doesn't seem to work, i.e. all records are counted but I only want those where Answer is true. Maybe its a syntax issue in my Linq, or my fundamental understanding is wrong.

 var count = _cosmosClient.GetContainer(DATABASE_ID, CONTAINER_ID)
                .GetItemLinqQueryable<ReportRecord>(true)
                .Count(r => r.Answer);

or

 var count = _cosmosClient.GetContainer(DATABASE_ID, CONTAINER_ID)
                .GetItemLinqQueryable<ReportRecord>(true)
                .Count(r => r.Answer == true);

For reference, the ReportRecord looks like this:

public class ReportRecord
    {
        public string Name { get; set; }
        public bool Answer { get; set; }
    }

If I switch to the asyn pattern below, then I can query successfully using the following, but I really want to use the sync pattern here for consistency.

List<ReportRecord> results = new List<ReportRecord>();
var container = _cosmosClient.GetContainer(DATABASE_ID, CONTAINER_ID);
var query = new QueryDefinition("SELECT * FROM Reports p WHERE p.answer = true");

using (FeedIterator<ReportRecord> resultSetIterator = container.GetItemQueryIterator<ReportRecord>(query))
{
     while (resultSetIterator.HasMoreResults)
     {
        FeedResponse<ReportRecord> response = await resultSetIterator.ReadNextAsync();
        results.AddRange(response);
     }
}

return results.Count;