I don't see why the number generated would be more likely to be cracked when the seed phrase has the same chance of being guessed.

Also when you use your seed phrase in the ian Coleman JS interface, the interface generate always the same addresses with the related private keys in the same order because this is deterministic. This is doing the same job as any other interface using the same protocol with the same seed phrase.
If I put the seed phrase in any other wallet, it will generate the exact same addresses in the same order with the same private keys. So on this side there is no difference between JS and the other software.