You said "That is why the Lord raised up Paul to present the "mystery" that had been hidden."
I assume you are talking about this.
"which in other generations was not made known to the sons of men, as it has now been revealed to His holy apostles and prophets in the Spirit;"
- Ephesians 3:5 NASB
Or you could be talking about this.
"[that is,] the mystery which has been hidden from the [past] ages and generations, but has now been manifested to His saints,"
- Colossians 1:26 NASB
It makes no difference as they were written at the same time. This is where Mid-Acts Dispensationalists divide history. For the record, Paul is discussing what was revealed through the gospel message forward [i.e. Pentecost forward], not what when Paul was incarcerated in Rome.
You compared Philip to a baby Christian wetting his pants in service of an argument for dry baptism. That's what brought this subject on. Nobody but a Mid-Acts Dispensationalists would do that.