That´s what I´m told as well. But I saw a video where a couple (and they must be champions the way they danced) rose to the balls of their feet. And they achived a very effective and nice looking rise and fall with it.
They accomplished a good balance by anchoring their free legs a little longer than normal.

My questions are:
Is it wrong to rise to the balls according to a technical guidance?

Since I don´t compete in Bolero I have little knowledge on judging technical issues.

If there is no such thing like a "technical bible" out there maybe there is more than way to dance it, depending on whom you ask!!??