Please read this thread Security risks of using Bitwarden as authenticator and password manager - #66 by mmja and my points in that thread.
You are absolutely right, storing them both inside same vault without extra protection is a serious security issue and should be avoided at all cost. I also made a thread Additional encryption for items protected by Master Password Reprompt about adding an additional encryption for items protected by Master Password prompt, this could mitigate, altought not remove, the problem of unprotected TOTP seeds store in Bitwarden…IF and only IF both additional password AND additional encryption based on that password is used to protect the TOTP. Otherwise it wont work…as the current “Master password prompt” currently is absolutely useless to really protect anything from anything, since its a software only solution right now.