...And doing all kinds of business confidential work for my employer or government ... and also looking at PII,financial,medical data of my own including SSNs and whatnot.

!!!

They take I think 30 pixels across known positions on the screen and that’s apparently enough to recognize content without being able to look at your confidential data.

Or video chatting with gf ...

Well then they know you're using Excel and probably want to be sold pension plans...

If you’re watching tv shows or movies that way, they know all the same. ACR works based on the image being displayed, not the source.

it's not a screenshot, they sample pixels and get essentially a CSV of the pixel values at several locations. There's then a content database with frame by frame values for those pixels for all the content in the database.

Sending a screenshot would use too much bandwidth/data on Samsung's side, but a couple dozen bytes every few minutes would not.