I will certainly agree that shoelaces are rather too small to work well as prussiks.
If "too small" means "too short" - I disagree. On my hiking boots they are almost 2 feet long - more than enough. Also one can improvise a lacing technique to have more cordage stored on your boots or to use less cordage for lacing when needed.
See here, for example.
In the climbing reference and context Hikemor was referring too and what he and I are both very familiar with, if the climbers had been engaged in rock climbing then they probably would not of been wearing hiking boots but wearing running or climbing shoes instead. Specialized rock climbing shoes usually have laces much like a running shoe which are much shorter then a typical hiking boot lace.
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Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn from books.
John Lubbock