"Do you know of any reason not to be splitting all parents that will qualify and double dip both the stimulus and the advance child tax credit."

Stop using the word "know." You are not asking about something Known. You are asking about something provided for

"Opinions get you no where in an audit"

If you know the rules, and want to take a position on which action to take, you don't need to keep asking anyone on the internet. If you did the research, stop hammering on about the issue.

I am going to make a guess, that you are uncomfortable with the provision and want some assurance that this will not bounce back at you and/or your clients. You would need to ask the IRS about that part.