The ISLOGICAL Function checks whether a value is logical value. When it is a logical value, the result returns to "TRUE", and returns "FALSE" when it is not.
Value is required, the result returns TRUE when the value is a logical value and returns False when it is not.
Cell A2 is True which is a logical value, so ISLOGICAL(A2) returns to True.
Cell A4 is the text "6F" which is not a logical value, so ISLOGICAL(A4) returns to False.