TLDR: string parsing is hard and most of us are vulnerable to assumptions and/or never get around to do those fuzzy tests properly when checking that input is handled correctly.
One of the vault backends has a size limit and so secret keys larger than 2048 bits would not fit. Amazing tool.
But I'm neither a security person nor have I done much with authentication since my 2000's PHP hobbying. I suspect an LDAP server has to deal with or try and manage a lot of garbage input because of the sheer number of integrations they often have.