Since you're a sensible person here, you're worthy of a sensible response unlike the children in the room.
It's the convenient way they craft the message to say Medicare for All. The majority of people they are targeting don't understand that as it relates to taxation. Notice how they will never mention "Were going to add a 10% income tax" or "Were going to impose a 15% Value added tax".... or really any commenting whatsoever on how it will be paid for. They are advertising and marketing it as free for the lower IQ individuals who don't even understand the tax withholding on their paystubs.... Which I can definitely say, there are plenty of people that look at their paycheck like it's in a foreign language other than the "Net Pay" portion. I'm not even saying that about poor/middle class folks, I've seen that plenty with well-educated engineers and accountants even heh.
Thus it is advertising as Free. Nothing is free. See quotes below from Bernie's website of a quick google. When you tell someone "Free at the point of service"4 and "no networks, no premiums, no deductibles, no copays" it doesn't at all give an indication to the actual people that reading that instead of a bill after service, they will see a continuous tax paid out on their paychecks.
The same was said below in relation to "debt-free public college" as they attempt to appeal to dumb students who racked up debt and implying that they will just magically make the concept of the debt go away....
Without digging way into the rabbit hole, every politician I have heard in moderately recent times (recent means within the last 25 years) has said some version of current personal and business insurance expenses will become taxes and there may be cuts to other parts of the budget or as Bernie and Warren said "yes there will be more taxes"
I seriously don't know anyone respectable who has claimed medicare for all would be free because reasons. I have heard the typical lunatic who makes outrageous claims who is not a policy maker or a candidate or an insurance expert or well any type of expert except in maybe collectible cards or manga or whatever make a claim that medicare for all would be free.
I have had deplorable friends make the claim sort of like you did in jest or an attempt to smear someone but even those guys know it is not what is being talked about.
Everyone understands medicare for all means what you pay for healthcare now becomes a tax meaning some would save money, some would spend more money and most would be more or less in the same position they currently are. The benefit isn't necessarily in the cost savings it is in the reliable coverage for all and no fear of an illness leading to bankruptcy, plus cutting all the irritating billing bullshit like in network vs out of network.
We literally have the most expensive healthcare in the world and we have mediocre results from our care vs dollars spent. There is no place in the world that runs healthcare like we do, there is no place in the world that runs a successful free market based health system.