I think SeekAndFind is substantially correct. Yes, you get Medicare Part A automaticity - and for free - when you turn 65.
But suppose you then, for whatever reason, refuse it. You write Medicare and tell them to take you off their Part A enrollee list. In that case, you would lose your social security benefits! Weird, huh?
No, I don't think that is weird. They need a guaranteed pool of covered people to keep the costs down.
And why would you overtly refuse it? Just ignore it and nothing will happen. It's free so you are not charged anything for it. What's the point in refusing it?
Yeah, I read the entire article at your link but it was 2015 vintage. And one of the complainants was Dick Armey, saying it interfered with his congressional medical insurance coverage which was superior. Oh, cry me a river. Spoiled elites. If Medicare is good for their constituents, then it should be good for them.
Writing to the Medicare and asking them to take you off the Part A enrollee list is an unforced error.
If they take your Social Security away because you did that, you deserve what happens.