I'm a Brit and a huge fan of Mo. I don't think Mo's is making excuses - he simply realises (as we all do) that he never has been and never will be as good as Geb or Bekele. He is the best example I can think of in sport of someone who has maximised his potential. He knew every year that an all-out WR attempt in the early or mid-season would reduce his chances of wining championship gold and he simply didn't have much margin for error. He was only marginally better than the rest over 5000 in 2011; Gebrmeskel should have beaten him in 2012; Gebriwhet should have been closer in 2013; a fit Ndiwa is probably as good as him over 5000m and a fit Kamworor is probably better than him over 10,000.
Knowing that WRs were out of reach, why interrupt heavy training to taper for an early or mid-season WR attempt? Geb and Bekele could get away with it because they could handle a much heavier racing schedule (even those of you who are convinced Mo uses PEDs have to accept that even if he does, he can't get away with the doping regimens of the pre-blood passport days).
FWIW, I think he's good for low 12:4xs at 5000. I think he's a little deluded in seeing himself as more of a 10,000 guy and think he could only run high 26:3xs (and suspect that Galen is only a second or two slower).