Yes, once you have 23 words, there is a finite set of possible words that can be used as the 24th to make checksum valid, and you could pick one at random. But

Yes, once you have 23 words, there is a finite set of possible words that can be used as the 24th to make checksum valid, and you could pick one at random. But as I understand the private key can be any number, so you do not need to even use the seed phrase technique to create a private key, or if you do it isn’t required that it has a valid checksum in order to operate on the network.