This is a myth, although it has some root in reality.
The best ideas are often borne out of the conviction of the founders and their ability to spot an untapped need.
Because of this, founders (and progenitors of the original idea) are often true believers... and they will execute harder and with more conviction (even if less effectively at first), because it was their idea in the first place.
They'll often have better reactions and can better see where the market is going, because it was their idea in the first place.
Depending on their personality, they may also be better able to conceive of and implement improvements, because it was their idea in the first place.
Execution is critically important, but one cannot exist without the other.
The best ideas are often borne out of the conviction of the founders and their ability to spot an untapped need.
Because of this, founders (and progenitors of the original idea) are often true believers... and they will execute harder and with more conviction (even if less effectively at first), because it was their idea in the first place.
They'll often have better reactions and can better see where the market is going, because it was their idea in the first place.
Depending on their personality, they may also be better able to conceive of and implement improvements, because it was their idea in the first place.
Execution is critically important, but one cannot exist without the other.