I haven't used a landline in years now, but when I was a kid it worked that way: one end hanging up wouldn't disconnect the circuit, and if the other end took the phone off-hook shortly afterwards it'd still be connected.
This would sometimes wind up being the deciding factor in the eternal battle of "which sibling gets to use the phone"
In my memory it never relied on both parties hanging up here in New Zealand, but on a trip to the UK as as child I noticed that the phone line disconnecting relied on both parties hanging up. I'm 31.
On landlines the call isn't finished until the caller hangs up. This allows features such as "call waiting" to work: the receiver flashes the hook in a certain way to switch to the other call. If flashing the hook would disconnect the call, "call waiting" wouldn't work.
It did at one time, and could still in some places. I can recall growing up in rural North Carolina in the late 70's and early 80's, when one party staying on the line, after the other hand hung up, would keep the connection open.
In the UK it does. On a standard BT residential line the caller can hold the call open even after the callee has put down the handset. When the callee lifts the handset again they won't be able to begin a new call until the caller terminates the call.
I also live in Scotland and I've had this happen to me in the past.
It almost never happens by accident - the person keeping the line open is paying for it, after all. (Or, traditionally, was, with bundles and free evening/weekend calls, I've no idea if people actually pay for landline calls any more.)
This would sometimes wind up being the deciding factor in the eternal battle of "which sibling gets to use the phone"