The roadside field sobriety test exists purely for the cop (s) to claim they saw further evidence you were intoxicated or under the influence and can be refused in most of not all states. It is never going to prove you are sober and is not in anyone’s best interests except the cop’s; check your state laws and never consent to the sobriety tests.
Similarly, the hand held portable breathalyzer can be refused in most of not all states, but if they (cop) decide to arrest you and bring you to the station then refusing the calibrated breathalyzer test machine (or blood or urine tests in some cases) there typically is worded as an admission of guilt in many states. Check your state laws and never agree to any breathalyzer unless doing so explicitly results in license forfeiture or implied admission of guilt. Even then, it may still be in a person’s best interests to refuse.
Assuming you’re talking about the handheld roadside units and not the calibrated stationary units, those ‘slight inaccuracies’ can be the difference between being let go or giving the cop any evidence to claim you’re intoxicated and hauling you into the station for processing. And again, the cop is only looking for excused to list as grounds for further suspicion and justification for hauling you in. Don’t do their jobs for them by voluntarily participating in any investigation that isn’t required by law.
If you’re referring to my comment about potentially refusing the breathalyzer at the station knowing it likely constitutes an admission of guilt; that can be the difference between being just over the limit or facing an Aggravated DUI charge for having a recklessly high BAC and finding out there are some distinct increases in penalties between the two. Realistically, someone with a BAC that puts them into Aggravated DUI territory isn’t likely to be thinking clearly enough to make that decision, but still with mentioning.
Obviously, no one should drink and drive in the first place, but if someone finds themselves in such a situation and is arrested it’s likely better to know the difference in consequences, legally.