Either way for California he wouldn't be affected because Californiamnproperty taxes are effectively snapshotted at time of purchase and grandfathered for people like him. If he truly bought or built 50 years ago and ows it outright then prop 13 has long capped what he pays decades ago.
People like him, in California, are subsidized by the modern generation who don't get capped by prop 13. And when he sells that house it's value gets assessed at current market value and full taxes are due from the buyer.
Put shortly, his story is likely bullshit if he's from California. And people without houses and salty about it need to do some research.
This doesn't fit the narrative, but a lot of American states have lower effective property tax rates than European nations. There exceptions on both ends of this of course (like TX which is making up for a lack of income taxes).
People should look them up and compare European nations to major us cities and states. Europe ends up with not only higher income taxes, but also higher property taxes overall. And a completely insane financing method like having adjustable rate mortgages being normal, locked only for a period of 3 to 5 years before basically being forced to refinance. Little wonder that property ownership rates are generally so far below american ownership rates.
No system is perfect and people with means tend to find every flaw in them (and plant those flaws if they are wealthy enough). But people really need to remember that the grass is always greener because of all the manure.