We heard about the planned crackdown by Transport on loads not secured properly mid last year. They emailed most med and larger buisnesses to let us know that they would be taking the existing regs seriously and enforcing them hard.
For boaties, that means properlly tied down loads front and rear. Not just winch cables and safety chains at front, the expected turnbuckles or something similar to hold it down. And straps holding the stern down.
I guess the prop thingy is just more of the same compliance. I usually have a flag on the prop but admit I dont use it all the time, will have to check if I can still find it and remember to use it all the time.
No big deal, just have to get into the habit of doing these things as part of the standard routine.