Meek bundle occasionally makes direct contact to Tor node.
I have been testing with meek transport bundle 3.6.2. I simply observed outbound connections with wireshark, and it was nearly always google's IP. But occasionally, it reaches out to a Tor node. In my case, it took 66 bytes from 184.108.40.206 which is a Tor node (checked with ExoneraTOR) I think this will let the traffic observer know you are connecting to tor network.