This method is called Limb Extension. I personally would never do it. It’s extremely painful, very expensive, and there’s a good chance you won’t be as active as you were. For a measly 3”! Bullsh*t!
I’m only doing height increase on the side. I’m not too dissatisfied with my height at 5’10 (178cm), but rather only want to hit the 180cm mark (I’m not dreaming about getting like 4 inches). My parents are 6’ and 5’7, and my father grew in his 20s. I have good reason to believe I may get a bit more height. If not, oh well.
I’ve heard about the calcium and growth plate thing. There’s no proof to it, people just say it. Besides, this growth plate being sealed or not doesn’t accurately predict whether you’re going to grow at all. My cousin went for an x-ray for a broken wrist at 17, his plates were said to be completely sealed. He still grew 2” at 20. All in the lower-body, as do all other growths after puberty. And I know plenty of guys who grew from 19-23.
I’m sure more guys grow into their 20s than we would know, but they just don’t take that opportunity. They have horrible lifestyles and sleep only after 4am. And as we know, sleep is essential to growth.
My verdict is, there’s a good to fair chance that you’ll grow if you try to, at this age. But generally don’t expect more than 1 or 2 inches.