Not an expert but I’ve heard this too. However - if this IS true, it’s definitely only true for the biggest drives, operating in huge arrays. I’ve been running a btrfs raid10 array of 4TB drives as a personal media and backup server for over a year, and it’s been going just fine. Recently one of the cheaper drives failed, and I replaced it with a higher quality NAS grade drive. Took about 2days to rebuild the array, but it’s been smooth sailing.