Not factual historically, and neither is the statement factual scripturally.
The original Person to sabbath the 7th day was God (Genesis 2:1-3, Exodus 20:8-11). Then also see:
Mar 2:27 And he said unto them, The sabbath was made for man, and not man for the sabbath:
Mar 2:28 Therefore the Son of man is Lord also of the sabbath.
The first "man" is Adam.
Then you can see many others long before Ellen G White who kept sabbath, the 7th day, including
Patrick Of Ireland (that's right, 'St.' Patrick).
Another long before Ellen G White:
Thomas Tillam:
Doctrine - Sabbath - Thomas Tillam - The Seventh Day Sabbath Sought Out -1657
https://ia801900.us.archive.org/35/items/doctrine-sabbath-thomas-tillam-the-seventh-day-sabbath-sought-out-1657/Doctrine - Sabbath - Thomas Tillam - The Seventh Day Sabbath Sought Out -1657.pdf
You might consider reading some historical sources (first hand, just making a kindly suggestion, really).