If it was merely ‘misremembering’ then millions would misremember the EXACT same way. You are correct. That would be impossible.
Some people would misremember Mandela dying in a car crash, or from an assassination, or any if the zillion ways to die. They would have misremembered it of different times. Some would misrembering him dying in the early 90s.
But no. There are two groups of people — millions of people split distinctly. And one of the two distinct group of millions of people ‘misremembers’ in exactly the same way. Exactly the same way. With 0 variation. Among millions of people.
The probability or even possibility of millions of people remembering anything the same way as each other must be incalculable.
Gaslight attempt?
CERN timeline fuckery?
Glitch in the simulation?
A sent alert signal?
A livestock tag?
Or all of them.