There are two or three controversial choices made in these books which might give you that impression. Remember, this method is meant for young, first-time students as a direct lead-in to the Rabbath books.
Vance proposed that 3rd and 4th position (i.e. at the heel and thumb position) were physically easier to begin with than traditional 1st position. That's because the left arm is awkwardly contorted to reach the lower notes, which most bassists are so used to that we don't even consider how strange it is for a beginner. Additionally, Vance was using the Laborie-style bent end pin, which can make playing and shifting in low positions even more unstable.
In order for 3rd position to make sense from the beginning, Vance also put quite a lot of emphasis on pivoting techniques. These are difficult for anyone not familiar or accustomed to it, regardless of general level.
A young beginner will accept whatever you show them, and I appreciate that the stigma of playing in thumb position, reading treble clef, and pivoting is immediately removed since it's introduced so early. Whether you believe that it's good pedagogy is an open question, but it is clear that many of Vance's original students went on to have brilliant careers.
