If the pilot follows the yellow line in a long aeroplane, the mainwheels will drag inside the turn by quite a distance. Therefore he should take the turn wide so the main body of the aeroplane more closely tracks the centreline. The less sharp the turn, the less care need be taken. But a widebody doing a 90 degree turn has to take great care.
At SFO, there are tight taxiway lines to parking gates and the problem may be that overshooting the turn could make you hit something. Such warnings are displayed prominently on charts.
I think you must be nearly qualified by now to a rather high degree!