The big deal is that higher voltages will pass straight through into you.
They're design is a terrible idea.
The screwdriver in the video was typical dangerous cheap Chinese shit. Standard 1/4W resistor barely rated at 250v for normal operation never mind where failure risks life. Not sure if I have one kicking around any more but I remember the resistor being much more substantial, probably 3/4" long with end caps and looking more like a small ceramic fuse.
As for higher voltage the clueless shouldn't be working with mains voltage never mind higher and there are not that many higher voltage sources the clueless have access to anyway.
It comes with a clip so you can carry in the a shirt pocket like a pen. It is a testing screwdriver meant to check the presence of mains so you can avoid working on it. I wouldn't have qualms about using a decent one to avoid the risk of finding out the hard way.
Yeah,back in the day,we used to sell well made ones at my first job-----I never liked them much,myself,but they were properly designed,with correct high voltage construction of the resistor,etc.
Ours were made in Germany,& had the maximum voltage rating clearly written on them.(380V)
They are meant to be used by people with some idea of what they are doing---not morons!