This was a pretty common trick to glitch slot machines, they are hardened quite a bit against this sort of trickery. A mobile phone is much more delicate in general construction and doesn't have access to a handy ground wire.
Devices that implement any restrictions against the end user like DRM or MDM, on the other hand, are in possession of the said user. I heard a saying that getting root privileges on a device you physically possess is only a matter of time and effort.
In other words, you can totally take your phone apart as much as your tools and skills allow, but you'll get arrested if you try taking a slot machine apart.
The idea was not to take the machine apart but to try to glitch it by hitting metal parts that were not properly grounded. This would then allow the voltage spike to make it into the circuitry, either leading to breakage, no effect, or fault injection. The latter could sometimes be converted into a win on a subsequent spin.
This is 80's stuff, I'm pretty sure todays' slot machines are tamper proof to the point that trying this is totally pointless, and even back then hardening against this was common.
They are. Source: I own a modern-ish computer based slot machine and tried my fair share of tricks against it.
Given the absence of mechanical reels and the fact that the components likely to be susceptible to glitching aren’t remotely close to the outside of the machine this isn’t a viable attack method for machines in operation.
Source: NV Tech Standard 1 [1] also have zapped modern slot machines with an ESD gun.
[1]: https://gaming.nv.gov/modules/showdocument.aspx?documentid=2...
I remember swiping the piezo lighters out of the gas heaters at highschool, and using them to glitch free games in Asteroids and PacMan machines...