Actually he did not.
We agree that sanctified is to be set apart.
We know a genuine beliver will be set apart, a non genuine beliver will not.
In the church of the time Hebrews as written not all were genuine belivers as we see today in our churches. People over here we call pew pushers.
Yet they call themselves Christian. In fact over here we have people who profess to be Christian on census forms because we are a country calls itself a Christian country (though this is now diminishing)
Jesus himself talks about and wheat and tares and said don't uproot.
Matthew 13:29-30
29 But he said, ‘No, lest while you gather up the tares you also uproot the wheat with them. 30 Let both grow together until the harvest, and at the time of harvest I will say to the reapers, “First gather together the tares and bind them in bundles to burn them, but gather the wheat into my barn.” ’ ”
So as I see it
@mailmandan is not saying that unbelievers are sanctified. They cannot be.
However you twist his words to support your doctrine that a genuine beliver can stop believing and use the passages in Hebrews to support your case.
As you say the OSAS at least say that a person was never a believer in the first place.
That's where you and others disagree with those who believe that.
Whilst that ok it's not but both camps will and post Bible verses to support their case.
But perverting and twisting what someone has said to support your case is not ok.