Beginnings of Sabbath Teaching

I would like to present two quotations just as a thought that I will follow up more on later as it distills in my mind. The first is a quotation from Ellen White from an early vision while the second is a couple of paragraphs of history. The first then:

There I was shown that the commandments of God, and. the testimony of Jesus Christ, relating to the shut door, could not be separated, and that the time for the commandments of God to shine out, with all their importance and for God's people to be tried on the Sabbath truth, was when the door w, as opened in the Most Holy Place of the Heavenly Sanctuary, where the Ark is, containing the ten commandments. This door was not opened, until the mediation of Jesus was finished in the Holy Place of the Sanctuary in 1844.

I saw that the present test on the Sabbath could not come, until the mediation of sins in the Holy Place was finished ; and he had passed within the second vail; therefore, Christians, who fell asleep before the door was opened in the Most Holy, when the midnight cry was finished, at the seventh month 1844 ; and had not kept the true Sabbath, now rest in hope; for they had not the light, and the test on the Sabbath, which we now have, since that door was opened. I saw that Satan was tempting some of God's people on this point. Because so many good Christians have fallen asleep in the triumphs of faith, and have not kept the true Sabbath, they were doubting about it being a test for us now. [The Present Truth August 1849 v1 #3]

The second is from the history of the Seventh day Baptists:

The study of the Scriptures in America brought Samuel and Tacy Hubbard to the Baptist principle of believer’s baptism in 1647, and membership in the First Baptist Church of Newport, Rhode Island. Beginning in 1665, their family and several others became convinced of the seventh day Sabbath and joined in fellowship with Stephen Mumford and his wife who had held Sabbath convictions while members of a Baptist church in Tewksbury, England. ...

A similar separation occurred in 1705 in Piscataway, New Jersey, when a deacon of the Baptist Church, Edmund Dunham, became convinced of the biblical basis for Sabbath observance. Dunham and sixteen others withdrew to form their own church. A third group of churches came out of the Keithian split from Quakerism in the Philadelphia area about 1700. ...

Did Ellen White mean to imply that the Sabbath was not introduced until 1844, and that light about the Sabbath was not available until Christ opened the door to and moved into the Most Holy Place after shutting the door to and leaving the Holy Place? After ending his mediation in the Holy Place (whatever that means...)?

Just a question...cause it looks like people were teaching about the Sabbath a long time before the Adventists latched onto it...