Yes, this is the culprit. This is a bug in the code since that PR.
You can workaround it by sneakily adding an extra executable option in the Redshift Deadline Plug-in for something that matches exactly that name without a number: Redshift_Executable_. If you know how to do that for Deadline plug-ins then at least you can ‘hotfix’ it and continue testing.
Actually an easier hotfix for now is just to set the REDSHIFT_VERSION env var for your Houdini application environment to 1.
Even if it would or would not - the Deadline Redshift plug-in wouldn’t pick it up. That entry is: Redshift_Executable_1 but due to the invalid submission we’re doing setting the version as "" it tries to look for Redshift_Executable_ instead, and fails because it does not exist.