hey! yes it is fine to do that. But out of curiosity, why do you want to maintain that format? Is the logic in your application API relying on this type of format?
Finally, we have a userID mapping feature as well which you can use to map supertokens userID to an externalUserId which is generally a better approach
SuperTokens is an open source authentication solution offering features like: Different types of login: Email / password, Passwordless (OTP or Magic link based).