I agree with you 100%. So much of the cult life in the organization is based on this concept. The idea that if something, at least at one time, was involved in a religion other than Jehovah's Witnesses it would be considered interfaith - literally worshiping a god other than Jehovah. Therefor being something that just was not done.
After leaving the organization I began to learn of customs practiced daily by Witnesses, at least in the U.S., that come from non-Judaeo-Christian religion.
Are you married?
Yes.
Did the bride wear a white gown?
Yes.
Were there bridesmaids and groomsmen?
Yes.
Are their wedding rings?
Yes.
All pagan ritual for weddings.
Here's the worst part - as an active Witness in the U.S. I dare you to go around your congregation stating that.
"Oh Brother So-and-So, is that a wedding band you're wearing? You do realize that is pagan in origin. You may want to take that off as to not stumble any one in the congregation."
"Sister So-and-So, I hear you are getting married this weekend. Are you having bridesmaids or wearing a white wedding dress? You shouldn't. Especially if you are having your wedding in the Kingdom Hall. Those are all practices steep in ancient false religion."
I promise you will be ordered to cease and desist under penalty of disfellowshipping if you don't.