Who says that?
Is it just because it works for you?
PS: Much sense? Does it make sense or not?
Look
When you play poker, the key to winning is to assess how your range performs against your opponents range. If its stronger you are ahead, if its weaker you are behind.
At any point in a hand you and your opponent each have a range for folding, calling and raising.
However in any given hand you have only one hand. Therefore sometimes your will hold the top of your range can your opponent holds the bottom of his and sometimes you hold the bottom of your range and he holds the top.
So sometimes you play a hand well and win, other times you play a hand well and lose.
However if your range is stronger than your opponents, then in the longrun you will always profit and if its weaker you will always lose.
Its because of that reason that poker skill cant be measured by playing a single hand, it can only be measured when you play a significant number of
hands.