Yes, because if you know where it is, you likely also know it's not wedged into a seat hinge getting crushed as you attempt to recline.

Overheating? Maybe. Preventing explosion? Absolutely.

It's not about the risk of it going up, but in whether it will be promptly noted and contained if it does go up.

I think the fear is that the user's phone is in the checked luggage.

At least in the USA, cell phones are allowed checked luggage. However, they are supposed to be powered of and "protected up prevent unintentional activation or damage".

I realize this was an Air France flight, but I suspect the checked rules are nearly the same.