I think it is a matter of both domain for how things fail and how reliability is defined. In some circumstances looser tolerances can be a bit less efficient but more fault tolerant and thus 'reliable'. Although its lifetime might also be shorter than a tighter toleranced device if both were fed 'clean' inputs.

Of course the fault tolerance (apologies for overloading the term tolerance) also isn't guaranteed in every domain. If a seal breaking would wreck the process it certainly wouldn't give /any/ reliability over a tight seal.