Step 4 in the decision tree appeared to be the ONLY place where the 1B factor of the ballpark is used, so I believe your current interpretation is not likely correct. The ballpark 1B factor is used in the calculation to determine hit or out, and then the HR, 2B, and 3B factors are used in later steps to influence whether a determined hit is one of those types. Any hit not determined to be a HR, 2B, or 3B then simply remains a single by default.