The user in question might have their own personal format that doesn't meet the RustDesk constraints. E.g. they may not use capitals, but use `word1$word2&word3@word4`.

Tayloring your format to the requirements of each site is a step towards defeating the utility of the system; now the user needs to remember some arbitrary hard-to-remember details for each password.

Although having a standard format for your passphrases across sites removes some of the advantages over just using the exact xkdc format (when one of your passwords is compromised and attackers can guess your custom format elsewhere now)...

This is a non-issue with a password manager