Ok Voltage sticks do work, but the whole concept of them is fundamentally flawed as a safety check and as a fault finder leave a lot to be desired
I am not really sure what is fundamentally flawed, from what I can see it is just detecting a time varying electric field. Which is actually similar in principal to a multimeter.
As a fault finder it is great in circumstances where you are tracing cables and you dont want to cut them or open a junction box to see if they are on a particular circuit.
In those cases it probably would be more risky to not use a volt stick.
Other safety issues with the multimeter method of testing for a live circuit are having your leads plugged wrongly and causing a short, having your leads not fully in and not realising it, having damaged leads but not knowing and maybe on some meters having the meter switched to DC instead of AC volts.
Also if you think that build construction is an issue then you need to think that build construction is an issue for any test equipment, especially test equipment that is making direct contact with live wires.
I think it is a great tool, mine is a fluke mark II, but I only use in certain situations, and as I was told once "You can trust it
if it is glowing".