No! It sounds like this guy is a car mechanic friend and not a lawn mower tech.
Unfortunately auto mechanics often do a lot more harm than good on the small engines because they're simply too different.
While I have heard of some odd things happening to the magnets on a flywheel that wasn't physical damage, because that's far more likely than anything else, from reverse polarization to demagnetization or weird things like that, I have NEVER seen one of these things happen for myself so I really don't believe most of the stories I've heard!
I have been running a shop commercially for 14 years now and have seen thousands upon thousands of mowers and these small engines.
While lots of things are possible.. most of these weird things are not very probable or likely at all.
And 99.8 or maybe more like 99.3% of the times, it will be something else rather than some crazy thing that it might be.
Most of the time if you start with the basic troubleshooting procedure, and if that's a good one because many people don't do it well or do it in a lousy order etc, you will rule out many other potential problems as you go and along the path quite quickly diagnose what the problem is.
In this situation, anytime you have concern about ignition, which should be the second thing you do and not the first... it's usually enough just to pull out the spark plug or two when it's a twin, and stick them back in the wires and ground the base of them to the block and crank it over to see if there's consistent spark going spark spark spark spark spark spark.
That rules out over 90% of the ignition problems including flywheels, coils, kill switches, magnets, igniters ...
However, you shouldn't be there first because it's often a waste of time.
The first thing to do, every time when you have a small engine that won't run , after you check the oil to make sure there's enough in there to safely start it and after you've determined that it will crank over at normal speed on its own or that you can pull the rope...is to give it an external fuel source.
This means dribbling a little bit of gas into the intake hole feeding the carburetor or spraying some carb cleaner in there or -if you must- I'm starting fluid but I highly discourage it because it is really rough on engines and just not necessary.
On a riding mower size engine, you spray a 2-second blast into the intake from the carb cleaner can and leave the choke in the open position if it has a manual choke which would be 3/4 on many throttle controls and not pushed all the way up.
Then you crank it for five or six seconds to see if it will run on its own for a couple of seconds.
If it doesn't do it the first time you repeat the spray of about 1 to 2 seconds and recrank.
It's also okay to do it a third time but if it doesn't run by the third time stop giving it the spray first. Now simply crank it over for 8 or 10 seconds with the choke open to see if it will try to run.
Probably at least 70 or 80% of the time when you do this, they will take off and run for 2 or 3 seconds.
Anytime this happens you can pretty much guarantee it's not getting fuel or feeding it on its own and it's usually the Jets and the carburetor are clogged up but it can also be ABS (solenoid) on the bottom of the carb, fuel pump if it has one, blockage in the gas tank or the fuel line or even a damaged and internally collapsed fuel line.
But the key point is if it runs for even a couple of seconds on your carb spray you have ruled out all kill switches, most ignition problems, and most valve train problems.
I have to say most because if it's a twin you could still have a bad coil or valve train problems on one head and it could be running on one cylinder.
Only if it doesn't do anything differently when you give it a fuel source do you start to check ignition and get into other things.
The most efficient diagnostic procedure is check the fuel delivery and give external fuel first.
Then check for ignition and consistent spark at each plug.
Then move on to removing the valve covers and check into the valve train.
