Well, he was wrong.
As an example, the very first batch of T/As known were ordered by Mr. Norms, so in the case T/As, ordered cars were built first, before sales bank cars.
The opposite is true for AARs.
Also, a whole lot more than 50% of both models were sales bank cars.
A dealer order ( or a client order through a dealership) in itself does not make it a special order in itself.
Something like 999 paint makes it a "special" order, otherwise it is just an "order".
Of all of the Mr. Norms records I saw for T/As, not even one of them was ordered by a client. The records are not complete, but I have seen over 100 of them.