Why does TA/UA cloning work with your proofreading HotStar HiFidelity DNA Polymerase?

QIAGEN's HotStar HiFidelity Polymerase Kit uses a novel high-fidelity DNA polymerase that was originally isolated from Pyrococcus spec.. It is a single enzyme (not a mixture of several different polymerases), and it was modified to generate an overhanging A needed for TA/UA cloning. Other proofreading enzymes do not create an A-overhang.