I really don´t know where you two get that from. Germany had 10 Panzer-Divisions not 12. However, the Polish and French campaigns has proved that the Panzer divisions were too heavily armored. Instead, they lacked supportive motorized infantry. Thats the reason why germany splitted the Divisions and added 1 more mot. Infantry-Regiment.
The new Tank-Divisions got around 30% more Tanks per Regiment than the old ones.
"Guderian said that he opposed Hitler's directive to split up existing divisions' panzer regiments, in order to double the number of panzer divisions. In Guderian's view, it decreased their power, while doubling the need for support equipment and personnel."
From his wiki page. Possible source
Guderian, Heinz (1952). Panzer Leader. New York
Sorry I was pulling 12 from memory. I knew it was around there