Will a dummy headset or old pair of clipped headphones do the same thing as Mic-Lock?Updated a month ago

This is a false belief and it doesn’t work.

All modern personal communication devices will not see two wires as a valid audio source.
To be a valid audio source an electrical signal is needed.

The seamless audio switch between internal and external audio is managed by the device's digital mix master.
This is what assigns the audio.

It cannot switch to nothing.

Mic-Lock provides the signal of silence back to the device.