..and curiously, with the little speaker icon 'on', it produces no audio alarm for me, (firefox 103.0.2). Whereas this[1] one produces a quite notable sound.
These days browsers make sure there's user interaction before audio plays. The other website you linked requires a click to start the timer, therefore meeting that requirement. If Google made this timer muted by default, and you had to click unmute, it would likely work.
Ran into a related bug on a site I was working on the other day and had to learn this browser quirk the hard way.
Ran into a related bug on a site I was working on the other day and had to learn this browser quirk the hard way.