My algorithms class taught to think of it not as "describing performance" in an absolute sense, but as "describing how performance changes as the size of the input data increases".
It is not necessarily true that an O(1) algorithm will outperform an O(n^2) alternative on a particular set of data. But it is true that an O(1) algorithm will outperform an O(n^2) alternative as the size of the input data increases.
It is not necessarily true that an O(1) algorithm will outperform an O(n^2) alternative on a particular set of data. But it is true that an O(1) algorithm will outperform an O(n^2) alternative as the size of the input data increases.