St. Peter illustrates this for us in Antioch. His personal sin led the rest of the Jews into sin in such a way that an essential doctrine was compromised. And it was indeed hypocrisy, not doctrinal error here. But I still think that this has no bearing on the apostolic Tradition which was passed down, preserved from error by God Himself, guided by the Holy Spirit. Maybe St. Peter was infallible in faith and morals, but his personal sin was leading his flock into damnably false doctrine.
Sin is always present, and scandal, sadly, is also far too often present.
When this occurs, some people will be led astray. There are other explanations for the development of the practice. Even today, it is very common for people to go to the graveyard and speak to their dead relatives. Given this common human tendency, there is no reason to invoke apostolic teaching to explain the phenomenon. Until you do, I say that your view is utterly implausible, and that these practices can only be deemed apostolic due to their earliness and widespread use, and the biblical indications.