Not only does the credit bureau max out their password length, you have a small list of available non-alphanumeric characters you can use, and no spaces. Also you cannot used a plused email address, and it had an issue with my self hosted email alias, forcing me to use my gmail address.
Both Experian and transunion had no password length limitations, nor did they require my username be my email address.
Update: I have been unable to log into my account for the last 3 days now. Every time I try I get a page saying to call customer service. After a total of 2 hours on hold I finally found the issue, you cannot connect to Equifax using a VPN. In addition there is no option for 2FA (not even email or sms) and they will hang up on you if you push the issue of their security being lax. Their reasoning for lax security and no vpn usage is "well all of our other customers are okay with this".
This implies they're storing the plaintext password.
Ideally the password would be hashed with a salt and then stored. Then it's a fixed length field and it shouldn't matter how long the password is.
Or a very very old database system, possibly DB2, where you can't change the column limits or data types after the fact.
If they're hashing, the column size should be irrelevant. Ideally the database should never see the plaintext password in the first place (though I could understand calculating the hash in the query itself). If they're not hashing, they should really be rewriting their database anyway.