I doubt Particular can do much about this. This is how Azure Functions scale controller works. Among various metrics, it looks at the queue depth over the time and oldest message age to decide wherever to scale out or not. If delayed/scheduled messages are in the queue, the scale controller doesn’t seem to know to differentiate those from normal messages, available for processing, confusing those for messages that can’t get processed and scaling out.
Unfortunately, the documentation on the scale controller is too minimalistic. I’ve raised an issue with the Functions to have a tracking public issue others can refer to and chime in/upvote.