1) It is not just BA who operates such a procedure; the 744 is capable of performing on 3, or even 2 engines, within safely defined performance criterea.
2) You doubt and refuse to accept what professionals say without being a pilot, based upon what - a gut reaction? These SOPs are proven and risk-based.
3) Whos to say that if the engine was working a valve still became stuck and prevented fuel flow, if that situation were to arise, or for that matter the same problem were to affect a 2-engined aircraft or an 8-engined aircraft.
4) You question the reputation of the professional crew without any basis for doing so, nor concrete evidence of the event.
5) An engine failure does not necessarily mean bits flying everywhere; equally a seriously destructive uncontained blade failure may not result in power loss initially. Many different causes and consequences all come among a power loss bracket.