That’s not the point. The point is we don’t need the silly “prophylactic” rule in Michigan vs Jackson in order to remedy involuntary waivers.
Sometimes witnesses lie when giving testimony. One way to avoid that happening is to not allow any witnesses to give any testimony, as a prophylactic rule.
Sometimes prosecutors bring charges against innocent people. One way to avoid that is to not allow prosecutors to bring charges against anyone, as a prophylactic rule.
And those examples are not so far beyond Michigan vs Jackson in their absurdity, to demonstrate the point.
In the case of very serious crimes, it is becoming standard practice in many jurisdictions to record police interrogations. So in these serious cases, we can typically expect there to be evidence for a judge to evaluate in deciding whether a waiver was voluntary - not merely a he said/he said situation. Michigan vs. Jackson goes way beyond what is necessary or reasonable, and certainly very far beyond what is constitutionally required.
People seem to get the idea these days, perhaps because of television shows, that any serious crime can be solved like magic by an attractive team of scientists applying highly sophisticated technology. In fact, many serious crimes would go unsolved if the perpetrator did not incriminate himself in speaking to investigators. Sometimes human beings feel the weight of guilt for their actions bearing them down, and there may be a brief moment when someone decides to take responsibility for what they have done when speaking to investigators. And at another point in time the same person may decide not to take responsibility but to try to get away with the crime, hoping the police do not have sufficient evidence to prevail against him. The only constitutional question pertaining to this particular issue is whether waiving presence of counsel and making statements to investigators was or was not voluntary.
Michigan vs Jackson is a silly and unnecessary rule, and certainly not constitutionally required.
If prosecutors and cops could be trusted to be honest and to only seek justice, Jackson would not be needed. Unfortunately too many of them can’t be trusted and are more interested in getting a conviction rather than making sure the right person is convicted.