You are absolutely right, but it's slightly off-topic, and I would be happy if my army consisted only of high-level vampires....
No, I'm not arguing; it would be cool if, for example, instead of a growth of 7 creatures, there was a growth of one, but in size 7. That's one thing. But it's impossible to do (while playing by the rules). That's why I phrased it that way. But it would be nice, of course. A growth of 70 vampires! That would be brutal.