These good olde boys last job was probably selling snake oil.
There are applications where magnetic types of water treatment seem to work. But probably not in once thru systems or at anything close to the consumer level.
These good olde boys know how to twist words. There have been tests where a chemical method was used as the baseline data reference and those results were compared to the "Effects" gotten by using some fancy magnetic whatever. The fun begins when they then have to prove the Effects.
The basic problem is most of the claims revolve around "Neutralizing the effects of the offending ions". They are not actually removed from the water like with most chemical systems. No such system has ever been demostrated to be effective AFAIK in something like your typical household water supply system or in just about any other once through type flow system.
There are some applications in a recirculating mode like boiler water treatment that apparently do work. I saw one very interesting system. Apparently the effect is limited in scale, maybe something as big as your typical packaged boiler. There are ranges on parameters that must be met. The water passes thru a treatment chamber many times. Uses the Earth's magnetic field. Would even descale a really badly gunked up boiler depending on the characteristics of how it got that way. The feedwater got tons of ions in it, you could never drink it, more like an ionic soup. Complicated but it does make a very nice war story.
There is also something known as paramagnetic and that type of principle is used in some applications. Like monitoring equipment to measure something. Oxygen is one of the things that is paramagnetic in properties. Very narrowly defined and applied but there are applications that work.
But if some olde boy claims to have invented the better mousetrap and it just happens to have a few magnets in it; and if he is talking about water and then that four letter word
PURE, head for the hills and hope your wallet has enough good sense to follow after you.
If I can invent a method to give you
PURE water, cost under $100 and look good on TV, I could be a very, very rich man. Ok, so you will settle for this sports bottled pure spring water, I just happen to have an extra 50 cases on hand this morning. It will even regrow hair on your behind in a topical fashion.
Just understand by definition
PURE WATER is probably deionized water (if you really want to be technical) and it will kill you if you manage to drink very much of it.