In my estimation, either one is, or is not, a genius. The key words in the post are "10,000 hours of focused practice". Not everyone is capable of that criteria of focused practice. If the ability is not there to begin with, no amount of focus will acheive the genius level of intellegence. On the other hand, some persons viewed by others as having "special needs", can, in fact, be highly intelligent to the point of being genius, yet remain outside the realm of most of the population's ability to recognize them as such.
On another front, we have all heard of twins separated at birth, growing up never knowing one another until years later. Some have literally lived within walking distance from one another, yet never met. But when their lives are examined, startling similarities come to the surface. Even though these twins were raised in separate households, with totally dissimilar family situations, they may wind up with the same tics, habits, even to the point of naming their children the same names, marrying people who are named the same, or developing the very same habits.
So, I fully believe the ability must be present in order to develop to the point of higher intellegence. Where you live, with whom you are raised, plays a much lesser part in our ability to learn than having the opportunity to advance our intellect. If the drive is there, the learning will occur. If it is absent, no amount of exterior force will create intellegence.