I understand that. I'm not disputing the fact that a 128 bit random integer is hard to guess.
The problem, however, is that it is being stored as a string. As such, if you decide to use the 32 character hex representation as a password, you're essentially storing a 32 character string that can only consist of 0-9a-f.
A random 32 character alphanumeric string would correspond to a random integer much larger than 128 bits, and as such, would be much stronger. There's no benefit to go with a weaker password.
The problem, however, is that it is being stored as a string. As such, if you decide to use the 32 character hex representation as a password, you're essentially storing a 32 character string that can only consist of 0-9a-f.
A random 32 character alphanumeric string would correspond to a random integer much larger than 128 bits, and as such, would be much stronger. There's no benefit to go with a weaker password.