Hmmm interesting! I go along with the theory it may be caused by bigger drums being fitted into normal size casings. I also had a tumble drier with a larger drum-good idea at the time. But within a few days of purchase the drum screeched after it had been operating for a short time. An engineer duly arrived who said the manufacturer was aware of the problem, caused by metal expansion then grating against the casing. Bigger drum but standard outer=screeching and grating when warmed up.
There was a modification kit engineer said, but when he looked it had already been fitted. So drier was exchanged without any fuss. But within a few short weeks exactly the same problem-the noise filled the house. Luckily I got a refund on that as problem was acknowledged by manufacturer. Now also got a Miele drier. Have spent soooo much money over the years on rubbish machines decided (after reading a lot of advice on here) to go for the best and cut my losses.