That one is a conventional pass regulator like you might find in any regulator circuit. The other transistor only has two connections. The design reverse ... a poor-quality Zener diode.

This is determined by the changes in input voltage through the diode. The output circuit amounts to a Zener regulator that switches from one Zener voltage to the other on transition through the Zener ...

Perhaps the simplest way to regulate a DC voltage is using a voltage divider and/or an active device like a Zener diode ... With careful design, though, a switching regulator can be constructed ...