Y'know vee-tail, I always wondered about that from when, back in about '71, I loaded some cadets in my car and we went to Brize to scrounge. A fresh crew took over after our flight and we stood and watched as an airman leaned against each propellor, and suddenly stepped away just as the prop started turning, so that explains it.
Would it I wonder, explain why a couple of years later at Glasgow, I witnessed numerous Monarch Brits starting at night with a huge jet of flame from the exhaust. I certainly never noticed anyone leaning against their props.