My friend once worked at a place where the security policy was that every part of the PC including monitors was crushed and shredded. This was a financial services company, but nevertheless totally over the top.
For example, lots of people don't realise how many printers are vulnerable to recovering previously printed documents. In the past, you might have just opened it up and ripped out the hard disk and memory, but nowadays with NAND and DRAM being soldered onto motherboards, do you really trust that's enough?
Had this been during something sensitive being displayed, it might warrant shredding that particular monitor. I have no idea how long the phantom image would have lasted. An hour, a day, a year?
Stored in the monitor control board somewhere.
Especially in the VRR era, monitors need to buffer the image in case it needs to be redrawn, or if the transfer rate is faster than the draw rate. Which will be anytime the monitor isn't drawing at max VRR sync speed.
You can either make hundreds of policies that discover where all this data is, or you make one policy that destroys everything.
I know which one has the least risk.