12 word seed phrase has 128 bits of entropy which is secure enough just like bitcoin private key. 24 words seed phrases have 256 bits of entropy, but yet having 128 bit of security.
Maybe I've misunderstood, but it reads to me like you're saying that a 12-word seed offers equivalent security (~128 bits) to that of the individual addresses generated from it, and that therefore, longer seeds are overkill.
Isn't that reasoning a little shaky? I mean, the seed is used to generate a unique
sequence of addresses [1], no? Putting aside the increased hassle of longer seeds, isn't it desirable for it to be harder to recover the sequence than it is to brute-force a single address?
[1] Technically, it's more like a tree than a sequence, but that's not germane.