No, it's not the SDA or other cults mandating it, it is God mandating it.
Salvation is not based on what day you keep, it is based on faith in Christ only.
Acts 16:31
King James Version
31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.
Eph
8 For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God—
9 not by works, so that no one can boast.
John 1:17 ESV
For the law was given through Moses; grace and truth came through Jesus Christ.
Romans 3:20-24 ESV
For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it— the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus,
Romans 4
1What shall we say then that Abraham our father, as pertaining to the flesh, hath found? 2For if Abraham were justified by works, he hath whereof to glory; but not before God. 3For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness. 4Now to him that worketh is the reward not reckoned of grace, but of debt. 5But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness. 6Even as David also describeth the blessedness of the man, unto whom God imputeth righteousness without works,
7Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered.
8Blessed is the man to whom the Lord will not impute sin.