HHRG and medicare billing

I was a home health field nurse for 2 years and I am familiar with the OASIS and HHRG scoring. I also understand HHRG was initiated in 2000 to establish a set payment after assessment of the patient so the HH agency could manage their care within that episode. I am now the HH Case Manager for a medicare advantage plan which follows the same exact medicare guidelines. I have been reading (and someone please help if you can) that all disciplines must complete their assessement of the patient for the accurate HHRG within 5 days of the first episode day........The problem I am having is that some agencies will send in an initial HHRG after the first OASIS (with a low score) after only the RN has seen the patient and get their authorization.....After that, they send in therapy evals and by the time they bill, there is a huge difference in payment request........Some are even doing therapy evals 21 days into the episode!......That can't be right, can it?........My agency that i worked for had all evals completed within 5 days, no if's and or but's........