I perfectly understand your argument.

Yes, the number of valid seeds is shrunk.
But that does not matter, because an attacker still needs to enumerate all seeds, in order to know if they are valid.
So, we are not reducing the size of the haystack.

It is as if you were claiming that the number of possible combinations is one because in the end there is only one seed that matches the private keys.
With that kind of reasoning, the entropy of anything is zero.

The problem is that you do not understand what entropy is. I think there is no point continuing this discussion.

Btw, raising the num_bits parameter to 132 would have no effect at all; math.ceil() already ensures that n is a multiple of 11 bits.