Not trying to argue that it is right, but isn't it pretty common for recovery vehicles on race tracks to leave the crane partially up when there is a car on the back?
I expect he's been given the hurry up by whoever wants him back in position, of off the race track, so that they can get back to the program asap.
If he's anyone that takes himself even half serious as a Truckie/Crane Op on the public road, he wouldn't even consider moving without totally folding up that crane.
I should point out that one of the cranes on a colleague's truck at my last job, was so packed full of safety sensors, moving the truck in this scenario would have had sensors laughing at the guy.
It could also be that he'd never had to drive under that gantry before and didn't know it was so low, but again, if you know your vehicle alarm bells should go off when approaching something so low.
They always post heights of bridges for example, but they don't ever do the same for low tree branches or electric/telephone wires.
The best I've ever encountered in that scenario is a general restriction on vehicles over a given height/weight.
Again, this is why it is so vital that you plan your route before you've even selected first gear.
Freight higher than your truck?
Know the height of your deck and measure your load before it goes on the deck, then do the sums.
Same applies for weight.
If the sender can't give you a document stating they've weighed and signed to say so, then it's on you to roll the dice or refuse to load.
One thing is for sure, the authorities will fine you a set fine for every given amount you're over, and can park you up in serious cases until they deem it is safe for you to continue.
I can only speak for Australia, mainly Victoria, but the fines for Truckies are so much higher when compared to drivers with a standard car licence, because we've had so much more training in order to obtain our licence, the general responsibility of operating such a vehicle in what is considered a public space, and what can happen when it goes horribly wrong.
The local Heavy National Vehicle Regulator, HNVR, have just spent forever reviewing and rewriting so many of the regulations, I'm kind of glad I'm out now. For those that are still working in the industry, it's on them to know the rulebook back to front with negligence unacceptable in any situation.