No, this isn't just confusion, this is a real behaviour difference between smartphones and (some) landlines. If someone calls you on a landline, depending on the exchange, hanging up your phone might not be enough to end the call; when you pick up again, you may still be connected to the caller.
It used to be the case that the party who made the call - being the party who is paying for it - was solely responsible for terminating it; then timeouts were introduced; and on many landline exchanges there is still a timeout before the call is actually terminated if the callee hangs up but the caller does not - although these days it is just a few seconds, that may still be long enough that you stay connected to the original caller if you hang up then immediately try to place a call.
It used to be the case that the party who made the call - being the party who is paying for it - was solely responsible for terminating it; then timeouts were introduced; and on many landline exchanges there is still a timeout before the call is actually terminated if the callee hangs up but the caller does not - although these days it is just a few seconds, that may still be long enough that you stay connected to the original caller if you hang up then immediately try to place a call.
Google "called party clear" for gory details.