No such thing as a "true" Christian

[Eleazar]

Of course, that said, it is believed that the original version of Mark 16 ended at verse eight, and that the next twelve verses were later additions.

Indeed - the earliest manuscripts we have don't include Mark 16:9-20, the language is thoroughly non-Markan, and it would be very strange for the gospel to end at verse 8. Most likely, the end of the scroll was simply lost (this was a common problem, because of the way scrolls were made - in fact, there are a number of important variants at the beginning of Mark's gospel too).