Thanks for noticing this. The correction has been made to the new document location: https://teiid.gitbooks.io/documents/content/reference/Spatial_Functions.html
There is a typo in the examples of functions: ST_AsText, ST_AsBinary, ST_AsGeoJSON, ST_AsGML.
Each of them contains 'Geom' in the name. ( ST_GeomAsText, ST_GeomAsBinary, ST_GeomAsGeoJSON, ST_GeomAsGML )