Do Protestant writers acknowledge the same?

Answer

They do.
NOTE - "IS there no express commandment for observing the first day of the week as Sabbath,
instead of the seventh day?-None whatever. Neither Christ, nor His apostles, nor the first Christians
celebrated the first day of the week instead of the seventh as the Sabbath."-New York Weekly Tribune,
May 24, 1900.
"The Scriptures nowhere call the first day of the week the Sabbath. . . . There is no Scriptural
authority for so doing, nor of course any Scriptural obligation." The Watchman (Baptist).
"The observance of the first instead of the seventh day rests on the testimony of the church, and
the church alone.' -- Hobart Church News, July 2, 1894.
For additional testimonies, see reading on page 146.

What test should therefore be applied to every professed teacher of truth?
Into whose name are believers to be baptized?
In what statement of the Scripture was Abraham's obedience really implied?
Who has borne our sins, and stands ready to help us?
What question was asked in the hearing of the prophet?
17. What prophetic period, therefore, extends to the deliverance of God's people from the captivity in modern Babylon, and the restoration to them of the mediation of Christ?
Was the Sabbath \"made\"?

Questions & Answers are from the book Bible Readings for the Home Circle