Airdog watching a game through binoculars is not making contact under any legal standard.   It may be a bit unnerving but it is legal.   The 4th doesn’t apply at all to this case.   I will agree that it wasn’t exactly a roust.   But the officers ‘advice’ was terrible.  He seems to be advocating breaking the law.   If the guy would have followed it and been subsequently arrested he would then have had a valid argument of entrapment.