Maybe something to do with seating position etc. that makes it difficult to adjust the mirror correctly. I use, and have always used, the method recommended in the link to adjust my door mirrors and the X1 mirrors seem to be able to accommodate both my wife and I with no problems albeit the drivers side is at the maximum clockwise position (when viewed from above the mirror) or very nearly.
2015 Glacier Silver 428i Gran Coupe
2015 British Racing Green Mini Cooper S 4 Door Hardtop
2012 Space Grey 528i MSport - retired
2013 Valencia Orange X1 xDrive 28i Msport - retired