Pega throws an exception in production if you have a flow in draft mode, but this is the worst possible time to find out that is the case! It has caused a number of headaches at our client due to (frankly) careless promotion of a draft flow, but there is otherwise no way to see it (other than reviewing the compliance log which has a high signal-to-noise ratio). Thus, the draft flow moves through each environment working as it should until it gets to the one environment that actually matters.
For the benefit of its customers, Pega needs to change this error to occur at any production level above development (2). This way, such things can be caught in QA/Test, where they should be caught, but Pega hides the issue until production, resulting in a lot of angry customers.
This is a simple change, and one I hope Pega can get into a near-term release.
Thanks for posting this enhancement @ColinCampbell! I have submitted this on your behalf in our internal system and updated your post with the FDBK ID. For next steps, please take the ID to your Account Executive.