Unless both sides hang up, there's something like a 10-20 second window where the call is held open. Hanging up, picking up within 10 seconds and dialing, means you're still connected to the original caller. If they're clever, the might even detect the click of you hanging up, and play a dialtone for when you pick back up, and stop playing it when you start to dial.

Citation needed. I don't recall any land line phone I've used behaving in this way.

I could see this working if the other end played a click followed by and dial tone sound.

No dial tone and no ring… Seems a difficult mistake to make but then again, I regularly surprise myself with my errors.

There's nothing technical that prevents the other side from playing dial tone and ring sounds