In reality, if you are using a narrow aperture or your subject is some distance away, you are unlikely to see issues using by recomposing. The effect gets worse as you use a wider aperture and/or the subject is closer.
Also at particularly wide angles, the wide field of view means that the act of recomposing itself can move the subject much further away from the lens.
It's also worse if your subject is moving, as they are likely to have moved out of focus in the time it takes to recompose.
I often have to do some recomposition as the 60D has 9 focus points...
On a mostly unrelated note I was using the canon 50mm f/1.4 on saturday at wide apertures and selecting focus point on still subjects about 10-12m away, and not recomposing and was still getting shots out of focus. I'm not normally one to proclaim my lenses are back/front focussing but the actual focus seemed to be about a metre closer than the point I actually focussed on with everything else being still, and no micro adjustment option on the 60D...
I think it is less to do with bad lenses and more to do with plane (ho ho) old physics. The plane of focus is just that.. a plane - so when you rotate the camera you are rotating the plane. When you recompose, the central point of that plane is still at the original distance, but that now needs to be moved closer to account for the fact that the plane on which the subject lies is now closer to the lens than it was before.
example of the plane of focus - but you have to use your imagination for the original plane of focus...
http://www.visual-vacations.com/Photography/focus-recompose_sucks.htm
No, the issue is with many fast lens (most of the f/1.4 primes but also many of the pro f/2.8 zooms) the focus plane isn't a plane at all but curved - called field curvature (all lenses suffer form it to some degree but some are much more pronounced). The field curvature is easily enough that someones head on the frame edge would be completely out of focus with a particular lens but completely in focus with a different lens both shot at the same aperture. The curvature can be pretty dramatic.
Your link is partly correct and partly wrong. yes, if you photograph a brick wall and the camera is parallel to the wall then in theory the whole image will be in focus including the far corners despite them being much further away than the center. That is the ideal design but that is hard to achieve. Most lenses can't actually project a flat plane like a wall onto a flat sensor maintain focus across the field.
that is where the article is wrong - almost all lenses have field curvature, it is basically impossible to avoid directly. What some lenses have is additional elements that try to correct for the field curvature which gives higher frequency lower amplitude distortions which at reasonable apertures is mostly invisible:
http://photographylife.com/what-is-field-curvature
But many fast lenses don't have these correcting elements for various reasons including negative affect Bokeh quality. So a fast prime lens design for portrait use may not be field curvature corrected so it is imperative to use the correct focus point nearest the subject. Similar some fast prime for portrait use omit apsherical element that correct for colour aberrations (different wavelengths focus at different lengths) because aspherical elements can make for harsh Bokeh.
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