I was not suggesting the original poster commit Fraud or Unethical behavior. The desired start date is one week and one day before the desired start date. I don't see any issues. If you search earlier posts sometime people are told they are too early and to come back to the POE closer to their start date. (usually this is two weeks or more, when they ask you to come back). If that happens, no big deal, you just have to make a second trip to the POE closer to your start date.
I agree start dates are tentative on a number of factors, background check, reference checks, drug tests, immigration authorization, etc. Any of these can delay a start date.
I was trying to say, in general, if you want to avoid the "your are too early" situation at the POE, have the TN support letter say you will start after TN status approval.