I get scared when my FO put their hand there during rotation right after I've removed mine!
(When I see that, I promptly put mine back again behind theirs to guard from a catastrophic mishap!!!)
If you are scared and don’t believe your FO, you should takeover and fly yourself, but not having both hands around thrust levers as it’s not standard procedure and you haven’t briefed it probably.
Also, putting your hands behind will make FO suprised and he will be looking what are you doing. You will be also focusing more then neccessary to thrust levers which means that both of you are not completely focused on instruments when you should be to the maximum.
Don’t invent procedures! That is one of the most dangerous things in aviation today.
Following your logic, do you have your hands behind levers also during short finals. What if your FO cuts power at 100ft?
Do you check where your FO holds his feet during TO when you are PF? Fully on pedals or heels on the floor?
Do you ever go out on a toilet during cruise, crossing Atlantic? Do you believe that your FO will handle engine fail correctly? Do you brief him before exiting cockpit?
There are too many ‘if situations’ and it’s impossible to guard against all of them.
Type rating should mean that you know how to operate the aircraft safely and in accordance with SOP. We all know there are better and worse guys, but most are in standard. Germanwings FO was probably quite standard FO....