Likelihood of casting rumours coming true

IMO some of the rumours we’ve heard regarding casting of the adults have been questionable at best (some good shouts though I.e. rylance). But thankfully all these at the moment are just RUMOURS.

Obviously it’s not productive or rational to dwell on them, but it’s just fun isn’t it - seeing as most of these will be in the series for the next 10 years.

Does anyone have any insights into the casting rumor history of other similar HBO shows or the original Harry Potter movies? Specifically, I’m curious about whether the initial rumors often matched the final cast or if there was a lot of speculation and false information circulating before the official announcements?