Actually your friend is likely taking something, though maybe not. There is a good amount of scientific / medical data and research on high altitude populations. Those genetics are very interesting, but the human physiological make up does not naturally support a hematocrit that high. There are other mechanisms at work for those who generationally have those genetics, but it is so obscenely rare for anyone to have over a 50% hematocrit let alone mid 50s.

You can read a good deal of medical data about Tibetan populations and climbers as well as many other high altitude genetics that don't support natural hematocrits EVER being that high. Ever. Ever. Ever.

Source my spouse is a hematologist and sports medicine specialist. She works for a Pro Tour team and specializes on altitude effects in endurance athletes. She also consults for WADA and has seen more tests than I can imagine. There are less than 6 pro tour riders who have medical exemptions for having a 52% red blood cell count or under. Triathlon has a fairly high percentage of people who attempt to apply for these exemptions. Its easy to see what is pure bullshit.