Lot of hedging in the various claims, I don't know anything about what 5 minutes of stretching will do before intense exercise - though I do believe that a quick stretch will not ameliorate improper technique in any physical activity.
I also believe - from my own experience - that yoga practiced regularly over the period of a year will bring greater flexibility and balance, even in a 58 year old.
I am taking about 4 yoga classes week now, and it seems to be paying off. Form what I understand, balance, flexibility, and strength should continue to improve for a number of years to come.