I know for a fact this is not true. Many people who became Adventist never read an Ellen White book, never had an SDA upbringing and from reading the Bible only and help of the Holy Sprit came to the same understandings. There is only one Gospel and one Truth in the scriptures. The Holy Sprit will lead you into all Truth if you're willing to do the will of God and not your own.
We have
@LoveGodsWord testimony who was not raised SDA, did not know of Ellen White. Pastor Doug lived in a cave and had no religious upbringing started reading the Bible and came to the same conclusion, so what you are saying is not true. There are many people who came to be Adventist that did not know EGW.
Here is Pastor Doug's personal Testimony
Two other pastors come to mind who came to the same conclusions Mark Finley and James Rafferty both former Catholics started reading the bible on their own and came to the same conclusions. There are thousands and thousands of members who have come to same the same conclusions just from reading the scriptures and not EGW.
And than we have Martin Luther:
I wonder exceedingly how it came to be imputed to me that I should reject the law of Ten Commandments...Whosoever abrogates the law must of necessity abrogate sin also.
—MARTIN LUTHER, Spiritual Antichrist, pages 71, 72.
and
The Sabbath was binding in Eden, and it has been in force ever since. This fourth commandment begins with the word 'remember,' showing that the Sabbath already existed when God wrote the law on the tables of stone at Sinai. How can men claim that this one commandment has been done away with when they will admit that the other nine are still binding?
—D.L. MOODY, Weighed and Wanting, page 47.
and
This 'handwriting of ordinances' our Lord did blot out, take away, and nail to His cross. (Colossians 2: 14.) But the moral law contained in the Ten Commandments, and enforced by the prophets, He did not take away.... The moral law stands on an entirely different foundation from the ceremonial or ritual law. ...Every part of this law must remain in force upon all mankind and in all ages.
—JOHN WESLEY, Sermons on Several Occasions, 2-Vol. Edition, Vol. I, pages 221, 222.