Maintaining "exactly" parallel feet

From a Workshop at Buffalo State College is a discussion of the rationale for maintaining "exactly" parallel feet. Also a picture of railroad tracks which are "exactly" 4',8.5" wide, so how far apart are the feet in Classical Tai Chi? The feet when parallel should be the length of one foot apart. So if you wear a size 8 shoe, or a 15 shoe the feet are exactly that length apart. Also, imagine a set of tracks that are exactly a size 8 or 15 wide and when parallel you could stand with left foot on one track and right foot on the other. If you began to turn either foot an inch you would start to fall off the track. Let me clarify that and say "rationale for maintaining exact... no, a better word is exactly parallel feet". I say "exactly" because the common thread is the emphasis on body mechanics and the concern about preserving and improving the health of the joints, such as those in the spine, hip, knee, and ankle. Parallel means side by side and having "exactly" the same distance continuously between them...no fudging and allowing either of the feet to even peek a little bit to the side.