Analogue telephones are creating (or at least in modern times simulating) a circuit, which doesn't close until the caller hangs up.

But almost everybody today has a digital phone, any kind of mobile telephone or desk VoIP phone is digital, "hanging up" ends the call because the telephone itself decided to do that, everything is just packets. So this trick won't be effective against most people today.

Likewise "dialling" today is an out-of-band digital step rather than a bunch of pulses or tones sent in-band that an attacker can just ignore.