Testing with the new parallelCollectionScan command and it looks like this command does not support the ability to limit the execution time of the operation.

I had expected it to work like the normal query operation were the cursor has a time limit associated with it that once exhausted causes a failure back to the client.

Is there a reason this functionality was left out?

I think all that would be needed would be to call setLeftoverMaxTimeMicros() based on a maxTimeMS within the command on the ClientCursor created on line 238 of parallel_collection_scan.cpp. https://github.com/mongodb/mongo/blob/master/src/mongo/db/commands/parallel_collection_scan.cpp#L238