The point about mprime is not that it puts so much more stress on the system.

The point about mprime is that it detects most errors due to internal checks of intermediate results.

Folding at home, for example, is not much less stress, but the reason why you see less errors is that errors that appear are not reported. You will only notice if the error damages anything vital to running the program, or if it messes up your OS. But any wrong computational results you will never notice.