ok, I hope this is my last post here.
So the easiest path to crack an Electrum private key is to just run through the 2^124 permutations, that is the shortest route.
That is precisely the point you are not getting.
How do you think an attacker can "run through" these 2^124 permutations?
Please try to focus on this question, and forget the rest.
First, let us agree that these are not "permutations".
In mathematics, a permutation is a bijective function between two sets.
However, the attacker does not have a simple function that takes integers up to 2^124 and maps them to the set of seeds accepted by is_new_seed().
So let us not talk about "permutations", but about "valid seeds".
So, how would an attacker "run throught" these 2^124 valid seeds?
The only way he can do that is to test all seeds, and to filter out the ones that are not valid.
That means the attacker has to enumerate a set of 2^132 seeds.