Ref T2015. This allows a maximum execution timeout to be set when running commands through Drydock. This change is pulled out of D10479, and this functionality is used when blueprints want to query the readiness of a host resource they've created, but don't want to stall forever if the remote host is not responsive.
This abbreviation seems unnecessary -- is "ExecTimeout" referencing anything specific? If not, let's call this "ExecutionTimeout"?
Much of this can now be rewritten to use %Ls more clearly and safely, see DiffusionSSHWorkflow for an example construction which does not require %C.