Although it's not as bad as the heat exchangers it's certainly not a non common issue in the ba btr. Mines done it....sister inlaws has done it and so has a mates. Also I hear it allot at work when people need new radiators due to same issue.
But as you say it is more known in the heat exchanger units especially earlier on in life.
I've herd of the FG haveing this exact issue with less then 1000ks on clock only a week old even
Some last 300 000ks aswell