This is the perfect example of what I was talking about, when you said: Pouring is definitely a biblical reference to receiving the Holy Spirit
I was referring to the nature of the baptism the example you gave is the extent of the Spirit. When the Holy Spirit takes up residence in a believer, He is part of our entire being. He seals us, He instructs us, He aids us and He gives us abilities. That is immersion in the Spirit.
The "pouring" out of the Spirit, is a picture word showing the extent. Perhaps what John Gill had to say might be of assistance to you.
John Gill:
By the Spirit is meant the gifts of the Spirit, the spirit of wisdom and knowledge, of understanding the mysteries of the Gospel, of explaining the Scriptures, and of speaking languages; and by the pouring of it out, is intended the abundance and great plenty of the gifts and graces of the Spirit bestowed; but yet not all of him, or all his gifts and grace in the large extent of them: therefore it is said, not "my Spirit", but "of my Spirit", or "out of it"; as out of an unfathomable, immeasurable, and inexhaustible fountain and fulness:
So as you can see, This has nothing to do with the issue of Baptism. But I think you knew that already.