The change to ros_control_boilerplate::GenericHWInterface was certainly unexpected.

[boilerbots]

Just so you know, removing the createTimer call for the update method in the GenericHWInterface constructor threw my project off track for a while until I tracked down the problem. It looks like the change is more than a year old but was not released to Melodic until September 2019.

At first it looked like the controller_manager couldn't start our controller anymore, it would hang and never respond. Here is the issue I created: ros-controls/ros_control#389

I am glad the fix was easy, once I found the problem.