At https://github.com/matrix-org/synapse/blob/develop/docs/workers.md (master is same in this regard at the moment) there exist 2 different regex endpoints for some endpoints. Mostly those that is also mentioned in stream writers has more regex matches than the otherwise same endpoint given earlier in generic worker list..

For example under generic worker listing:

# Device requests
^/_matrix/client/(r0|v3|unstable)/sendToDevice/

and then later in stream writer to_device listing:

^/_matrix/client/(api/v1|r0|v3|unstable)/sendToDevice/